FIELD OF THE INVENTION
[0001] The invention relates to methods for transmitting channel quality reports and/or
sounding reference symbols from a mobile station to a base station. The invention
is also providing the mobile station and the base station for performing the methods
described herein.
TECHNICAL BACKGROUND
Long Term Evolution (LTE)
[0002] Third-generation mobile systems (3G) based on WCDMA radio-access technology are being
deployed on a broad scale all around the world. A first step in enhancing or evolving
this technology entails introducing High-Speed Downlink Packet Access (HSDPA) and
an enhanced uplink, also referred to as High Speed Uplink Packet Access (HSUPA), giving
a radio access technology that is highly competitive.
[0003] In order to be prepared for further increasing user demands and to be competitive
against new radio access technologies, 3GPP introduced a new mobile communication
system which is called Long Term Evolution (LTE). LTE is designed to meet the carrier
needs for high speed data and media transport as well as high capacity voice support
for the next decade. The ability to provide high bit rates is a key measure for LTE.
[0004] The work item (WI) specification on Long-Term Evolution (LTE) called Evolved UMTS
Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN)
is finalized as Release 8 (LTE Rel. 8). The LTE system represents efficient packet-based
radio access and radio access networks that provide full IP-based functionalities
with low latency and low cost. In LTE, scalable multiple transmission bandwidths are
specified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order to achieve flexible
system deployment using a given spectrum. In the downlink, Orthogonal Frequency Division
Multiplexing (OFDM) based radio access was adopted because of its inherent immunity
to multipath interference (MPI) due to a low symbol rate, the use of a cyclic prefix
(CP) and its affinity to different transmission bandwidth arrangements. Single-carrier
frequency division multiple access (SC-FDMA) based radio access was adopted in the
uplink, since provisioning of wide area coverage was prioritized over improvement
in the peak data rate considering the restricted transmit power of the user equipment
(UE). Many key packet radio access techniques are employed including multiple-input
multiple-output (MIMO) channel transmission techniques and a highly efficient control
signaling structure is achieved in LTE Rel. 8/9.
LTE architecture
[0005] The overall architecture is shown in Fig. 1 and a more detailed representation of
the E-UTRAN architecture is given in Fig. 2. The E-UTRAN consists of an eNodeB, providing
the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations
towards the user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY), Medium
Access Control (MAC), Radio Link Control (RLC) and Packet Data Control Protocol (PDCP)
layers that include the functionality of user-plane header-compression and encryption.
It also offers Radio Resource Control (RRC) functionality corresponding to the control
plane. It performs many functions including radio resource management, admission control,
scheduling, enforcement of negotiated uplink Quality of Service (QoS), cell information
broadcast, ciphering/deciphering of user and control plane data, and compression/decompression
of downlink/uplink user plane packet headers. The eNodeBs are interconnected with
each other by means of the X2 interface.
[0006] The eNodeBs are also connected by means of the S1 interface to the EPC (Evolved Packet
Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME
and to the Serving Gateway (SGW) by means of the S1-U. The S1 interface supports a
many-to-many relation between MMEs/Serving Gateways and eNodeBs. The SGW routes and
forwards user data packets, while also acting as the mobility anchor for the user
plane during inter-eNodeB handovers and as the anchor for mobility between LTE and
other 3GPP technologies (terminating S4 interface and relaying the traffic between
2G/3G systems and PDN GW). For idle state user equipments, the SGW terminates the
downlink data path and triggers paging when downlink data arrives for the user equipment.
It manages and stores user equipment contexts, e.g. parameters of the IP bearer service,
network internal routing information. It also performs replication of the user traffic
in case of lawful interception.
[0007] The MME is the key control-node for the LTE access-network. It is responsible for
idle mode user equipment tracking and paging procedure including retransmissions.
It is involved in the bearer activation/deactivation process and is also responsible
for choosing the SGW for a user equipment at the initial attach and at time of intra-LTE
handover involving Core Network (CN) node relocation. It is responsible for authenticating
the user (by interacting with the HSS). The Non-Access Stratum (NAS) signaling terminates
at the MME and it is also responsible for generation and allocation of temporary identities
to user equipments. It checks the authorization of the user equipment to camp on the
service provider's Public Land Mobile Network (PLMN) and enforces user equipment roaming
restrictions. The MME is the termination point in the network for ciphering/integrity
protection for NAS signaling and handles the security key management. Lawful interception
of signaling is also supported by the MME. The MME also provides the control plane
function for mobility between LTE and 2G/3G access networks with the S3 interface
terminating at the MME from the SGSN. The MME also terminates the S6a interface towards
the home HSS for roaming user equipments.
Component Carrier Structure in LTE (Release 8)
[0008] The downlink component carrier of a 3GPP LTE (Release 8) is subdivided in the time-frequency
domain in so-called subframes. In 3GPP LTE (Release 8) each subframe is divided into
two downlink slots as shown in Fig. 3, wherein the first downlink slot comprises the
control channel region (PDCCH region) within the first OFDM symbols. Each subframe
consists of a give number of OFDM symbols in the time domain (12 or 14 OFDM symbols
in 3GPP LTE (Release 8)), wherein each OFDM symbol spans over the entire bandwidth
of the component carrier. The OFDM symbols thus each consists of a number of modulation
symbols transmitted on respective

subcarriers as also shown in Fig. 4.
[0009] Assuming a multi-carrier communication system, e.g. employing OFDM, as for example
used in 3GPP Long Term Evolution (LTE), the smallest unit of resources that can be
assigned by the scheduler is one "resource block". A physical resource block (PRB)
is defined as

consecutive OFDM symbols in the time domain (e.g. 7 OFDM symbols) and

consecutive subcarriers in the frequency domain as exemplified in Fig. 4 (e.g. 12
subcarriers for a component carrier). In 3GPP LTE (Release 8), a physical resource
block thus consists of

resource elements, corresponding to one slot in the time domain and 180 kHz in the
frequency domain (for further details on the downlink resource grid, see for example
3GPP TS 36.211, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels
and Modulation (Release 8)", section 6.2, available at http://www.3gpp.org and incorporated
herein by reference).
[0010] One subframe consists of two slots, so that there are 14 OFDM symbols in a subframe
when a so-called "normal" CP (cyclic prefix) is used, and 12 OFDM symbols in a subframe
when a so-called "extended" CP is used. For sake of terminology, in the following
the time-frequency resources equivalent to the same

consecutive subcarriers spanning a full subframe is called a "resource block pair",
or equivalent "RB pair" or "PRB pair".
[0011] The term "component carrier" refers to a combination of several resource blocks in
the frequency domain. In future releases of LTE, the term "component carrier" is no
longer used; instead, the terminology is changed to "cell", which refers to a combination
of downlink and optionally uplink resources. The linking between the carrier frequency
of the downlink resources and the carrier frequency of the uplink resources is indicated
in the system information transmitted on the downlink resources.
[0012] Similar assumptions for the component carrier structure apply to later releases too.
Carrier Aggregation in LTE-A for support of wider bandwidth
[0013] The frequency spectrum for IMT-Advanced was decided at the World Radio communication
Conference 2007 (WRC-07). Although the overall frequency spectrum for IMT-Advanced
was decided, the actual available frequency bandwidth is different according to each
region or country. Following the decision on the available frequency spectrum outline,
however, standardization of a radio interface started in the 3rd Generation Partnership
Project (3GPP). At the 3GPP TSG RAN #39 meeting, the Study Item description on "Further
Advancements for E-UTRA (LTE-Advanced)" was approved. The study item covers technology
components to be considered for the evolution of E-UTRA, e.g. to fulfill the requirements
on IMT-Advanced.
[0014] The bandwidth that the LTE-Advanced system is able to support is 100 MHz, while an
LTE system can only support 20 MHz. Nowadays, the lack of radio spectrum has become
a bottleneck of the development of wireless networks, and as a result it is difficult
to find a spectrum band which is wide enough for the LTE-Advanced system. Consequently,
it is urgent to find a way to gain a wider radio spectrum band, wherein a possible
answer is the carrier aggregation functionality.
[0015] In carrier aggregation, two or more component carriers (component carriers) are aggregated
in order to support wider transmission bandwidths up to 100MHz. Several cells in the
LTE system are aggregated into one wider channel in the LTE-Advanced system which
is wide enough for 100 MHz even though these cells in LTE are in different frequency
bands.
[0016] All component carriers can be configured to be LTE Rel. 8/9 compatible, at least
when the aggregated numbers of component carriers in the uplink and the downlink are
the same. Not all component carriers aggregated by a user equipment may necessarily
be Rel. 8/9 compatible. Existing mechanism (e.g. barring) may be used to avoid Rel-8/9
user equipments to camp on a component carrier.
[0017] A user equipment may simultaneously receive or transmit one or multiple component
carriers (corresponding to multiple serving cells) depending on its capabilities.
A LTE-A Rel. 10 user equipment with reception and/or transmission capabilities for
carrier aggregation can simultaneously receive and/or transmit on multiple serving
cells, whereas an LTE Rel. 8/9 user equipment can receive and transmit on a single
serving cell only, provided that the structure of the component carrier follows the
Rel. 8/9 specifications.
[0018] Carrier aggregation is supported for both contiguous and non-contiguous component
carriers with each component carrier limited to a maximum of 110 Resource Blocks in
the frequency domain using the 3GPP LTE (Release 8/9) numerology.
[0019] It is possible to configure a 3GPP LTE-A (Release 10) compatible user equipment to
aggregate a different number of component carriers originating from the same eNodeB
(base station) and of possibly different bandwidths in the uplink and the downlink.
The number of downlink component carriers that can be configured depends on the downlink
aggregation capability of the UE. Conversely, the number of uplink component carriers
that can be configured depends on the uplink aggregation capability of the UE. It
may not be possible to configure a mobile terminal with more uplink component carriers
than downlink component carriers.
[0020] In a typical TDD deployment, the number of component carriers and the bandwidth of
each component carrier in uplink and downlink is the same. Component carriers originating
from the same eNodeB need not to provide the same coverage.
[0021] The spacing between centre frequencies of contiguously aggregated component carriers
shall be a multiple of 300 kHz. This is in order to be compatible with the 100 kHz
frequency raster of 3GPP LTE (Release 8/9) and at the same time preserve orthogonality
of the subcarriers with 15 kHz spacing. Depending on the aggregation scenario, the
n x 300 kHz spacing can be facilitated by insertion of a low number of unused subcarriers
between contiguous component carriers.
[0022] The nature of the aggregation of multiple carriers is only exposed up to the MAC
layer. For both uplink and downlink there is one HARQ entity required in MAC for each
aggregated component carrier. There is (in the absence of SU-MIMO for uplink) at most
one transport block per component carrier. A transport block and its potential HARQ
retransmissions need to be mapped on the same component carrier.
[0023] The Layer 2 structure with activated carrier aggregation is shown in Fig. 5 and Fig.
6 for the downlink and uplink respectively.
[0024] When carrier aggregation is configured, the mobile terminal only has one RRC connection
with the network. At RRC connection establishment/re-establishment, one cell provides
the security input (one ECGI, one PCI and one ARFCN) and the non-access stratum mobility
information (e.g. TAI) similarly as in LTE Rel. 8/9. After RRC connection establishment/re-establishment,
the component carrier corresponding to that cell is referred to as the downlink Primary
Cell (PCell). There is always one and only one downlink PCell (DL PCell) and one uplink
PCell (UL PCell) configured per user equipment in connected state. Within the configured
set of component carriers, other cells are referred to as Secondary Cells (SCells);
with carriers of the SCell being the Downlink Secondary Component Carrier (DL SCC)
and Uplink Secondary Component Carrier (UL SCC). The characteristics of the downlink
and uplink PCell are:
- For each SCell the usage of uplink resources by the UE, in addition to the downlink
ones is configurable; the number of DL SCCs configured is therefore always larger
or equal to the number of UL SCCs, and no SCell can be configured for usage of uplink
resources only
- The uplink PCell is used for transmission of Layer 1 uplink control information
- The downlink PCell cannot be de-activated, unlike SCells
- From UE perspective, each uplink resource only belongs to one serving cell
- The number of serving cells that can be configured depends on the aggregation capability
of the UE
- Re-establishment is triggered when the downlink PCell experiences Rayleigh fading
(RLF), not when downlink SCells experience RLF
- The downlink PCell cell can change with handover (i.e. with security key change and
RACH procedure)
- Non-access stratum information is taken from the downlink PCell
- PCell can only be changed with handover procedure (i.e. with security key change and
RACH procedure)
- PCell is used for transmission of PUCCH
[0025] The configuration and reconfiguration of component carriers can be performed by RRC.
Activation and deactivation is done via MAC control elements. At intra-LTE handover,
RRC can also add, remove, or reconfigure SCells for usage in the target cell. When
adding a new SCell, dedicated RRC signaling is used for sending the system information
of the SCell, the information being necessary for transmission / reception (similarly
as in Rel-8/9 for handover).
[0026] When a user equipment is configured with carrier aggregation there is one pair of
uplink and downlink component carriers that is always active. The downlink component
carrier of that pair might be also referred to as 'DL anchor carrier'. Same applies
also for the uplink.
[0027] When carrier aggregation is configured, a user equipment may be scheduled over multiple
component carriers simultaneously but at most one random access procedure shall be
ongoing at any time. Cross-carrier scheduling allows the PDCCH of a component carrier
to schedule resources on another component carrier. For this purpose a component carrier
identification field is introduced in the respective DCI formats, called CIF.
[0028] A linking between uplink and downlink component carriers allows identifying the uplink
component carrier for which the grant applies when there is no-cross-carrier scheduling.
The linkage of downlink component carriers to uplink component carrier does not necessarily
need to be one to one. In other words, more than one downlink component carrier can
link to the same uplink component carrier. At the same time, a downlink component
carrier can only link to one uplink component carrier.
LTE RRC states
[0029] LTE is based on only two main states: "RRC_IDLE" and "RRC_CONNECTED".
[0030] In RRC_IDLE the radio is not active, but an ID is assigned and tracked by the network.
More specifically, a mobile terminal in RRC_IDLE performs cell selection and reselection
- in other words, it decides on which cell to camp. The cell (re)selection process
takes into account the priority of each applicable frequency of each applicable Radio
Access Technology (RAT), the radio link quality and the cell status (i.e. whether
a cell is barred or reserved). An RRC_IDLE mobile terminal monitors a paging channel
to detect incoming calls, and also acquires system information. The system information
mainly consists of parameters by which the network (E-UTRAN) can control the cell
(re)selection process. RRC specifies the control signalling applicable for a mobile
terminal in RRC_IDLE, namely paging and system information. The mobile terminal behaviour
in RRC_IDLE is specified in TS 36.304, incorporated herein by reference.
[0031] In RRC_CONNECTED the mobile terminal has an established RRC connection with contexts
in the eNodeB. The E-UTRAN allocates radio resources to the mobile terminal to facilitate
the transfer of (unicast) data via shared data channels. To support this operation,
the mobile terminal monitors an associated control channel which is used to indicate
the dynamic allocation of the shared transmission resources in time and frequency.
The mobile terminal provides the network with reports of its buffer status and of
the downlink channel quality, as well as neighbouring cell measurement information
to enable E-UTRAN to select the most appropriate cell for the mobile terminal. These
measurement reports include cells using other frequencies or RATs. The UE also receives
system information, consisting mainly of information required to use the transmission
channels. To extend its battery lifetime, a UE in RRC_CONNECTED may be configured
with a Discontinuous Reception (DRX) cycle. RRC is the protocol by which the E-UTRAN
controls the UE behaviour in RRC_CONNECTED.
[0032] Fig. 7 shows a state diagram with an overview of the relevant functions performed
by the mobile terminal in IDLE and CONNECTED state.
Logical and Transport Channels
[0033] The MAC layer provides a data transfer service for the RLC layer through logical
channels. Logical channels are either Control Logical Channels which carry control
data such as RRC signalling, or Traffic Logical Channels which carry user plane data.
Broadcast Control Channel (BCCH), Paging Control channel (PCCH), Common Control Channel
(CCCH), Multicast Control Channel (MCCH) and Dedicated Control Channel (DCCH) are
Control Logical Channels. Dedicated Traffic channel (DTCH) and Multicast Traffic Channel
(MTCH) are Traffic Logical Channels.
[0034] Data from the MAC layer is exchanged with the physical layer through Transport Channels.
Data is multiplexed into transport channels depending on how it is transmitted over
the air. Transport channels are classified as downlink or uplink as follows. Broadcast
Channel (BCH), Downlink Shared Channel (DL-SCH), Paging Channel (PCH) and Multicast
Channel (MCH) are downlink transport channels, whereas the Uplink Shared Channel (UL-SCH)
and the Random Access Channel (RACH) are uplink transport channels.
[0035] A multiplexing is then performed between logical channels and transport channels
in the downlink and uplink respectively.
Layer 1/Layer 2 (L1/L2) Control Signaling
[0036] In order to inform the scheduled users about their allocation status, transport format
and other data-related information (e.g. HARQ information, transmit power control
(TPC) commands), L1/L2 control signaling is transmitted on the downlink along with
the data. L1/L2 control signaling is multiplexed with the downlink data in a subframe,
assuming that the user allocation can change from subframe to subframe. It should
be noted that user allocation might also be performed on a TTI (Transmission Time
Interval) basis, where the TTI length can be a multiple of the subframes. The TTI
length may be fixed in a service area for all users, may be different for different
users, or may even by dynamic for each user. Generally, the L1/2 control signaling
needs only be transmitted once per TTI. Without loss of generality, the following
assumes that a TTI is equivalent to one subframe.
[0037] The L1/L2 control signaling is transmitted on the Physical Downlink Control Channel
(PDCCH). A PDCCH carries a message as a Downlink Control Information (DCI), which
includes resource assignments and other control information for a mobile terminal
or groups of UEs. In general, several PDCCHs can be transmitted in one subframe.
[0038] It should be noted that in 3GPP LTE, assignments for uplink data transmissions, also
referred to as uplink scheduling grants or uplink resource assignments, are also transmitted
on the PDCCH.
[0039] With respect to scheduling grants, the information sent on the L1/L2 control signaling
may be separated into the following two categories, Shared Control Information (SCI)
carrying Cat 1 information and Downlink Control Information (DCI) carrying Cat 2/3
information.
Shared Control Information (SCI) carrying Cat 1 information
[0040] The shared control information part of the L1/L2 control signaling contains information
related to the resource allocation (indication). The shared control information typically
contains the following information:
- A user identity indicating the user(s) that is/are allocated the resources.
- RB allocation information for indicating the resources (Resource Blocks (RBs)) on
which a user(s) is/are allocated. The number of allocated resource blocks can be dynamic.
- The duration of assignment (optional), if an assignment over multiple sub-frames (or
TTIs) is possible.
[0041] Depending on the setup of other channels and the setup of the Downlink Control Information
(DCI) - see below - the shared control information may additionally contain information
such as ACK/NACK for uplink transmission, uplink scheduling information, information
on the DCI (resource, MCS, etc.).
Downlink Control Information (DCI) carrying Cat 2/3 information
[0042] The downlink control information part of the L1/L2 control signaling contains information
related to the transmission format (Cat 2 information) of the data transmitted to
a scheduled user indicated by the Cat 1 information. Moreover, in case of using (Hybrid)
ARQ as a retransmission protocol, the Cat 2 information carries HARQ (Cat 3) information.
The downlink control information needs only to be decoded by the user scheduled according
to Cat 1. The downlink control information typically contains information on:
- Cat 2 information: Modulation scheme, transport-block (payload) size or coding rate,
MIMO (Multiple Input Multiple Output)-related information, etc. Either the transport-block
(or payload size) or the code rate can be signaled. In any case these parameters can
be calculated from each other by using the modulation scheme information and the resource
information (number of allocated resource blocks)
- Cat 3 information: HARQ related information, e.g. hybrid ARQ process number, redundancy
version, retransmission sequence number
[0043] Downlink control information occurs in several formats that differ in overall size
and also in the information contained in its fields. The different DCI formats that
are currently defined for LTE are described in detail in 3GPP TS 36.212, "Multiplexing
and channel coding ", section 5.3.3.1 (available at http://www.3gpp.org and incorporated
herein by reference).
Uplink Control Information (UCI)
[0044] In general, uplink control signaling in mobile communication systems can be divided
into two categories:
- Data-associated control signaling, is control signaling which is always transmitted
together with uplink data and is used in the processing of that data. Examples include
transport format indications, "New data" Indicator (NDIs) and MIMO parameters.
- Control signaling not associated with data is transmitted independently of any uplink
data packet. Examples include HARQ Acknowledgements (ACK/NACK) for downlink data packets,
Channel Quality Indicators (CQIs) to support link adaptation, and MIMO feedback such
as Rank Indicators (RIs) and Precoding Matrix Indicators (PMI) for downlink transmissions.
Scheduling Requests (SRs) for uplink transmissions also fall into this category.
[0045] Uplink data-associated control signaling is not necessary in LTE, as the relevant
information is already known to the eNodeB. Therefore, only data-non-associated control
signaling exists in the LTE uplink.
[0046] Consequently, the UCI can consist of:
- Scheduling Requests (SRs)
- HARQ ACK/NACK in response to downlink data packets on the PDSCH (Physical Downlink
Shared CHannel). One ACK/NACK bit is transmitted in the case of single-codeword downlink
transmission while two ACK/NACK bits are used in the case of two-codeword downlink
transmission.
- Channel State Information (CSI) which includes CQIs as well as the MIMO-related feedback
consisting of RIs and PMI. 20 bits per subframe are used for the CSI
[0047] The amount of UCI a UE can transmit in a subframe depends on the number of SC-FDMA
symbols available for transmission of control signaling data. The PUCCH supports eight
different formats, depending on the amount of information to be signaled. The following
UCI formats on PUCCH are supported, according to the following overview
PUCCH Format |
Uplink Control Information (UCI) |
Format 1 |
Scheduling Request (SR) (unmodulated waveform) |
Format 1a |
1-bit HARQ ACK/NACK with/without SR |
Format 1b |
2-bit HARQ ACK/NACK with/without SR |
Format 2 |
CSI (20 coded bits) |
Format 2 |
CSI and 1- or 2-bit HARQ ACK/NACK for extended CP only |
Format 2a |
CSI and 1-bit HARQ ACK/NACK (20 + 1 coded bits) |
Format 2b |
CSI and 2-bit HARQ ACK/NACK (20 + 2 coded bits) |
Format 3 |
Multiple ACK/NACKs for carrier aggregation: up to 20 ACK/NACK bits plus optional SR,
in 48 coded bits |
[0048] Using the different defined PUCCH formats (according to 5.4.1 and 5.4.2 of TS 36.211),
the following combinations of UCI on PUCCH are supported (see Section 10.1.1 of TS
36.213):
- Format 1a for 1-bit HARQ-ACK or in case of FDD for 1-bit HARQ-ACK with positive SR
- Format 1 b for 2-bit HARQ-ACK or for 2-bit HARQ-ACK with positive SR
- Format 1b for up to 4-bit HARQ-ACK with channel selection when the UE is configured
with more than one serving cell or, in the case of TDD, when the UE is configured
with a single serving cell
- Format 1 for positive SR
- Format 2 for a CSI report when not multiplexed with HARQ-ACK
- Format 2a for a CSI report multiplexed with 1-bit HARQ-ACK for normal cyclic prefix
- Format 2b for a CSI report multiplexed with 2-bit HARQ-ACK for normal cyclic prefix
- Format 2 for a CSI report multiplexed with HARQ-ACK for extended cyclic prefix
- Format 3 for up to 10-bit HARQ-ACK for FDD and for up to 20-bit HARQ-ACK for TDD
- Format 3 for up to 11-bit corresponding to 10-bit HARQ-ACK and 1-bit positive/negative
SR for FDD and for up to 21-bit corresponding to 20-bit HARQ-ACK and 1-bit positive/negative
SR for TDD.
- Format 3 for multi-cell HARQ-ACK, 1-bit positive/negative SR and a CSI report for
one serving cell.
Downlink & Uplink Data Transmission
[0049] Regarding downlink data transmission, L1/L2 control signaling is transmitted on a
separate physical channel (PDCCH), along with the downlink packet data transmission.
This L1/L2 control signaling typically contains information on:
- The physical resource(s) on which the data is transmitted (e.g. subcarriers or subcarrier
blocks in case of OFDM, codes in case of CDMA). This information allows the mobile
terminal (receiver) to identify the resources on which the data is transmitted.
- When user equipment is configured to have a Carrier Indication Field (CIF) in the
L1/L2 control signaling, this information identifies the component carrier for which
the specific control signaling information is intended. This enables assignments to
be sent on one component carrier which are intended for another component carrier
("cross-carrier scheduling"). This other, cross-scheduled component carrier could
be for example a PDCCH-less component carrier, i.e. the cross-scheduled component
carrier does not carry any L1/L2 control signaling.
- The Transport Format, which is used for the transmission. This can be the transport
block size of the data (payload size, information bits size), the MCS (Modulation
and Coding Scheme) level, the Spectral Efficiency, the code rate, etc. This information
(usually together with the resource allocation (e.g. the number of resource blocks
assigned to the user equipment)) allows the user equipment (receiver) to identify
the information bit size, the modulation scheme and the code rate in order to start
the demodulation, the de-rate-matching and the decoding process. The modulation scheme
may be signaled explicitly.
- Hybrid ARQ (HARQ) information:
■ HARQ process number: Allows the user equipment to identify the hybrid ARQ process
on which the data is mapped.
■ Sequence number or new data indicator (NDI): Allows the user equipment to identify
if the transmission is a new packet or a retransmitted packet. If soft combining is
implemented in the HARQ protocol, the sequence number or new data indicator together
with the HARQ process number enables soft-combining of the transmissions for a PDU
prior to decoding.
■ Redundancy and/or constellation version: Tells the user equipment, which hybrid
ARQ redundancy version is used (required for de-rate-matching) and/or which modulation
constellation version is used (required for demodulation).
- UE Identity (UE ID): Tells for which user equipment the L1/L2 control signaling is
intended for. In typical implementations this information is used to mask the CRC
of the L1/L2 control signaling in order to prevent other user equipments to read this
information.
[0050] To enable an uplink packet data transmission, L1/L2 control signaling is transmitted
on the downlink (PDCCH) to tell the user equipment about the transmission details.
This L1/L2 control signaling typically contains information on:
- The physical resource(s) on which the user equipment should transmit the data (e.g.
subcarriers or subcarrier blocks in case of OFDM, codes in case of CDMA).
- When user equipment is configured to have a Carrier Indication Field (CIF) in the
L1/L2 control signaling, this information identifies the component carrier for which
the specific control signaling information is intended. This enables assignments to
be sent on one component carrier which are intended for another component carrier.
This other, cross-scheduled component carrier may be for example a PDCCH-less component
carrier, i.e. the cross-scheduled component carrier does not carry any L1/L2 control
signaling.
- L1/L2 control signaling for uplink grants is sent on the DL component carrier that
is linked with the uplink component carrier or on one of the several DL component
carriers, if several DL component carriers link to the same UL component carrier.
- The Transport Format, the user equipment should use for the transmission. This can
be the transport block size of the data (payload size, information bits size), the
MCS (Modulation and Coding Scheme) level, the Spectral Efficiency, the code rate,
etc. This information (usually together with the resource allocation (e.g. the number
of resource blocks assigned to the user equipment)) allows the user equipment (transmitter)
to pick the information bit size, the modulation scheme and the code rate in order
to start the modulation, the rate-matching and the encoding process. In some cases
the modulation scheme maybe signaled explicitly.
- Hybrid ARQ information:
■ HARQ Process number: Tells the user equipment from which hybrid ARQ process it should
pick the data.
■ Sequence number or new data indicator: Tells the user equipment to transmit a new
packet or to retransmit a packet. If soft combining is implemented in the HARQ protocol,
the sequence number or new data indicator together with the HARQ process number enables
soft-combining of the transmissions for a protocol data unit (PDU) prior to decoding.
■ Redundancy and/or constellation version: Tells the user equipment, which hybrid
ARQ redundancy version to use (required for rate-matching) and/or which modulation
constellation version to use (required for modulation).
- UE Identity (UE ID): Tells which user equipment should transmit data. In typical implementations
this information is used to mask the CRC of the L1/L2 control signaling in order to
prevent other user equipments to read this information.
[0051] There are several different possibilities how to exactly transmit the information
pieces mentioned above in uplink and downlink data transmission. Moreover, in uplink
and downlink, the L1/L2 control information may also contain additional information
or may omit some of the information. For example:
- HARQ process number may not be needed, i.e. is not signaled, in case of a synchronous
HARQ protocol.
- A redundancy and/or constellation version may not be needed, and thus not signaled,
if Chase Combining is used (always the same redundancy and/or constellation version)
or if the sequence of redundancy and/or constellation versions is pre-defined.
- Power control information may be additionally included in the control signaling.
- MIMO related control information, such as e.g. pre-coding, may be additionally included
in the control signaling.
- In case of multi-codeword MIMO transmission transport format and/or HARQ information
for multiple code words may be included.
[0052] For uplink resource assignments (on the Physical Uplink Shared Channel (PUSCH)) signaled
on PDCCH in LTE, the L1/L2 control information does not contain a HARQ process number,
since a synchronous HARQ protocol is employed for LTE uplink. The HARQ process to
be used for an uplink transmission is given by the timing. Furthermore, it should
be noted that the redundancy version (RV) information is jointly encoded with the
transport format information, i.e. the RV info is embedded in the transport format
(TF) field. The Transport Format (TF) respectively modulation and coding scheme (MCS)
field has for example a size of 5 bits, which corresponds to 32 entries. 3 TF/MCS
table entries are reserved for indicating redundancy versions (RVs) 1, 2 or 3. The
remaining MCS table entries are used to signal the MCS level (TBS) implicitly indicating
RV0. The size of the CRC field of the PDCCH is 16 bits.
[0053] For downlink assignments (PDSCH) signaled on PDCCH in LTE the Redundancy Version
(RV) is signaled separately in a two-bit field. Furthermore the modulation order information
is jointly encoded with the transport format information. Similar to the uplink case
there is 5 bit MCS field signaled on PDCCH. 3 of the entries are reserved to signal
an explicit modulation order, providing no Transport format (Transport block) info.
For the remaining 29 entries modulation order and Transport block size info are signaled
.Channel Quality ReportingThe principle of link adaptation is fundamental to the design of a radio interface
which is efficient for packet-switched data traffic. Unlike the early versions of
UMTS (Universal Mobile Telecommunication System), which used fast closed-loop power
control to support circuit-switched services with a roughly constant data rate, link
adaptation in LTE adjusts the transmitted data rate (modulation scheme and channel
coding rate) dynamically to match the prevailing radio channel capacity for each user.
[0054] For the downlink data transmissions in LTE, the eNodeB typically selects the modulation
scheme and code rate (MCS) depending on a prediction of the downlink channel conditions.
An important input to this selection process is the Channel State Information (CSI)
feedback transmitted by the User Equipment (UE) in the uplink to the eNodeB.
[0055] Channel state information is used in a multi-user communication system, such as for
example 3GPP LTE to determine the quality of channel resource(s) for one or more users.
In general, in response to the CSI feedback the eNodeB can select between QPSK, 16-QAM
and 64-QAM schemes and a wide range of code rates. This CSI information may be used
to aid in a multi-user scheduling algorithm to assign channel resources to different
users, or to adapt link parameters such as modulation scheme, coding rate or transmit
power, so as to exploit the assigned channel resources to its fullest potential.
[0056] The CSI is reported for every component carrier, and, depending on the reporting
mode and bandwidth, for different sets of subbands of the component carrier. In 3GPP
LTE, the smallest unit for which channel quality is reported is called a subband,
which consists of multiple frequency-adjacent resource blocks.
[0057] As described before, user equipments will usually not perform and report CSI measurements
on configured but deactivated downlink component carriers but only radio resource
management related measurements like RSRP (Reference Signal Received Power) and RSRQ
(Reference Signal Received Quality).
[0058] Commonly, mobile communication systems define special control signalling that is
used to convey the channel quality feedback. In 3GPP LTE, there exist three basic
elements which may or may not be given as feedback for the channel quality. These
channel quality elements are:
- MCSI: Modulation and Coding Scheme Indicator, sometimes referred to as Channel Quality
Indicator (CQI) in the LTE specification
- PMI: Precoding Matrix Indicator
- RI: Rank Indicator
[0059] The MCSI suggests a modulation and coding scheme that should be used for transmission,
while the PMI points to a pre-coding matrix/vector that is to be employed for spatial
multiplexing and multi-antenna transmission (MIMO) using a transmission matrix rank
that is given by the RI. Details about the involved reporting and transmission mechanisms
are given in the following specifications to which it is referred for further reading
(all documents available at http://www.3gpp.org and incorporated herein by reference):
- 3GPP TS 36.211, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels
and modulation", version 10.0.0, particularly sections 6.3.3, 6.3.4,
- 3GPP TS 36.212, "Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing
and channel coding", version 10.0.0, particularly sections 5.2.2, 5.2.4, 5.3.3,
- 3GPP TS 36.213, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer
procedures", version 10.0.1, particularly sections 7.1.7, and 7.2.
[0060] In 3GPP LTE, not all of the above identified three channel quality elements are reported
at any time. The elements being actually reported depend mainly on the configured
reporting mode. It should be noted that 3GPP LTE also supports the transmission of
two codewords (i.e. two codewords of user data (transport blocks) may be multiplexed
to and transmitted in a single sub-frame), so that feedback may be given either for
one or two codewords. The individual reporting modes for the aperiodic channel quality
feedback are defined in 3GPP LTE.
[0061] The periodicity and frequency resolution to be used by a UE to report on the CSI
are both controlled by the eNodeB. The Physical Uplink Control Channel (PUCCH) is
used for periodic CSI reporting only (i.e. CSI reporting with a specific periodicity
configured by RRC); the PUSCH is used for aperiodic reporting of the CSI, whereby
the eNodeB specifically instructs (by a PDCCH) the UE to send an individual CSI report
embedded into a resource which is scheduled for uplink data transmission.
[0062] In addition, in case of multiple transmit antennas at the eNodeB, CSI values(s) may
be reported for a second codeword. For some downlink transmission modes, additional
feedback signaling consisting of Precoding Matrix Indicators (PMI) and Rank Indications
(RI) is also transmitted by the UE.
[0063] In order to acquire CSI information quickly, eNodeB can schedule aperiodic CSI by
setting a CSI request bit in an uplink resource grant sent on the Physical Downlink
Control Channel.
[0064] In 3GPP LTE, a simple mechanism is foreseen to trigger the so-called aperiodic channel
quality feedback from the user equipment. An eNodeB in the radio access network sends
a L1/L2 control signal to the user equipment to request the transmission of the so-called
aperiodic CSI report (see 3GPP TS 36.212, section 5.3.3.1.1 and 3GPP TS 36.213, section
7.2.1 for details). Another possibility to trigger the provision of aperiodic channel
quality feedback by the user equipments is linked to the random access procedure (see
3GPP TS 36.213, section 6.2).
[0065] Whenever a trigger for providing channel quality feedback is received by the user
equipment, the user equipment subsequently transmits the channel quality feedback
to the eNodeB. Commonly, the channel quality feedback (i.e. the CSI report) is multiplexed
with uplink (user) data on the Physical Uplink Shared CHannel (PUSCH) resources that
have been assigned to the user equipment by L1/L2 signalling by the scheduler (eNodeB).
In case of carrier aggregation, the CSI report is multiplexed on those PUSCH resources
that have been granted by the L1/L2 signal (i.e. the PDCCH) which triggered the channel
quality feedback.
Sounding Reference Symbol (SRS)
[0066] The SRS are important for uplink channel sounding to support dynamic uplink resource
allocation, as well as for reciprocity-aided beamforming in the downlink. Release
10 introduces the possibility of dynamically triggering individual SRS transmissions
via the PDCCH; these dynamic aperiodic SRS transmissions are known as "type-1" SRSs,
while the Release 8 periodic RRC-configured SRSs are known as "type-0" in Relase 10.
[0067] An indicator in an uplink resource grant on the PDCCH can be used to trigger a single
type 1 SRS transmission. This facilitates rapid channel sounding to respond to changes
in traffic or channel conditions, without typing up SRS resources for a long period.
In DCI format 0, one new bit can indicate activation of a type 1 SRS according to
a set of parameters that is configured beforehand by RRC signaling. In DCI format
4, which is used for scheduling uplink SU-MIMO transmissions, two new bits allow one
of three sets of RRC-configured type 1 SRS transmission parameters to be triggered.
[0068] The SRS transmissions are always in the last SC-FDMA symbol of the corresponding
subframe where reporting is configured/scheduled. PUSCH data transmission is not permitted
on the SC-FDMA signal designated for SRS, i.e. PUSCH transmission is punctured such
that all symbols but the last are used for PUSCH.
Uplink Control Signaling and Multiplexing
[0069] When simultaneous uplink PUSCH data and control signaling are scheduled, the control
signaling is normally multiplexed together with the data (in PUSCH) prior to the DFT
spreading, in order to preserve the single-carrier low Cubic Metric (CM) property
of the uplink transmission. The uplink control channel, PUCCH, is used by a UE to
transmit any necessary control signaling only in subframes in which the UE has not
been allocated any RBs for PUSCH transmission.
[0070] Further information on the multiplexing of the uplink control signaling can be found
in Chapters 16.3.1.1, 16.3.3, 16.3.4, 16.3.5, 16.3.6, 16.3.7, 16.4 of
LTE - The UMTS Long Term Evolution - From Theory to Practice, Edited by Stefanie Sesia,
Issam Toufik, Matthew Baker, Second Edition, incorporated herein by reference
DRX (Discontinuous Reception)
[0071] In order to provide reasonable battery consumption of user equipment, 3GPP LTE (Release
8/9) as well as 3GPP LTE-A (Release 10) provides a concept of discontinuous reception
(DRX). Technical Standard TS 36.321 Chapter 5.7 explains the DRX and is incorporated
by reference herein.
[0072] The following parameters are available to define the DRX UE behavior; i.e. the periods
at which the mobile node is active (i.e. in Active Time), and the periods where the
mobile node is not active (i.e. in Non-Active Time, while in DRX mode).
- On duration (timer): duration in downlink sub-frames that the user equipment, after waking up from DRX
(Non-Active Time), receives and monitors the PDCCH. If the user equipment successfully
decodes a PDCCH, the user equipment stays awake and starts the DRX Inactivity Timer;
[1-200 subframes; 16 steps: 1-6, 10-60, 80, 100, 200]
- DRX Inactivity Timer: duration in downlink sub-frames that the user equipment waits to successfully decode
a PDCCH, from the last successful decoding of a PDCCH; when the UE fails to decode
a PDCCH during this period, it re-enters DRX. The user equipment shall restart the
DRX Inactivity Timer following a single successful decoding of a PDCCH for a first
transmission only (i.e. not for retransmissions). [1-2560 subframes; 22 steps, 10
spares: 1-6, 8, 10-60, 80, 100-300, 500, 750, 1280, 1920, 2560]
- DRX Retransmission timer: specifies the number of consecutive PDCCH subframes where a downlink retransmission
is expected by the UE after the first available retransmission time. [1-33 subframes,
8 steps: 1, 2, 4, 6, 8, 16, 24, 33]
- DRX short cycle: specifies the periodic repetition of the on duration followed by a possible period
of inactivity for the short DRX cycle. This parameter is optional. [2-640 subframes
; 16 steps: 2, 5, 8, 10, 16, 20, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640]
- DRX short cycle timer: specifies the number of consecutive subframes the UE follows the short DRX cycle
after the DRX Inactivity Timer has expired. This parameter is optional.[1-16 subframes]
- Long DRX Cycle Start offset: specifies the periodic repetition of the on duration followed by a possible period
of inactivity for the DRX long cycle as well as an offset in subframes when on-duration
starts (determined by formula defined in TS 36.321 section 5.7); [cycle length 10-2560
subframes; 16 steps: 10, 20, 30, 32, 40, 64, 80, 128, 160, 256, 320, 512, 640, 1024,
1280, 2048, 2560; offset is an integer between [0 - subframe length of chosen cycle]]
[0073] The total duration that the UE is awake is called "Active time". The Active Time
includes the OnDuration time of the DRX cycle, the time UE is performing continuous
reception while the DRX Inactivity Timer has not expired and the time UE is performing
continuous reception while waiting for a downlink retransmission after one HARQ RTT.
Similarly for the uplink, UE is awake at the subframes where Uplink retransmissions
grants can be received, i.e. every 8ms after initial uplink transmission until maximum
number of retransmissions is reached. Based on the above the minimum active time is
of length equal to on-duration, and the maximum is undefined (infinite). Furthermore
also after having sent an SR on the PUCCH UE will be awake monitoring for a PDCCH
allocating UL-SCH Conversely, the Non-Active Time is basically the the duration of
downlink subframes during which a UE can skip reception of downlink channels for battery
saving purposes.
[0074] The operation of DRX gives the mobile terminal the opportunity to deactivate the
radio circuits repeatedly (according to the currently active DRX cycle) in order to
save power. Whether the UE indeed remains in Non-Active Time (i.e. is not active)
during the DRX period may be decided by the UE; for example, the UE usually performs
inter-frequency measurements which cannot be conducted during the On-Duration, and
thus need to be performed some other time.
[0075] The parameterization of the DRX cycle involves a trade-off between battery saving
and latency. On the one hand, a long DRX period is beneficial for lengthening the
UE's battery life. For example, in the case of a web browsing service, it is usually
a waste of resources for a UE continuously to receive downlink channels while the
user is reading a downloaded web page. On the other hand, a shorter DRX period is
better for faster response when data transfer is resumed - for example when a user
requests another web page.
[0076] To meet these conflicting requirements, two DRX cycles - a short cycle and a long
cycle - can be configured for each UE. The transition between the short DRX cycle,
the long DRX cycle and continuous reception is controlled either by a timer or by
explicit commands from the eNB. In some sense, the short DRX cycle can be considered
as a confirmation period in case a late packet arrives, before the UE enters the long
DRX cycle - if data arrives at the eNB while the UE is in the short DRX cycle, the
data is scheduled for transmission at the next wake-up time and the UE then resumes
continuous reception. On the other hand, if no data arrives at the eNB during the
short DRX cycle, the UE enters the long DRX cycle, assuming that the packet activity
is finished for the time being.
[0077] Available DRX values are controlled by the network and start from non-DRX up to x
seconds. Value x may be as long as the paging DRX used in IDLE. Measurement requirement
and reporting criteria can differ according to the length of the DRX interval i.e.
long DRX intervals may experience more relaxed requirements.
[0078] When DRX is configured, periodic CQI/SRS reports shall only be sent by the UE during
the "active-time". RRC can further restrict periodic CQI reports so that they are
only sent during the on-duration.
[0079] In Fig. 8 a per-subframe example of the DRX cycle is shown. The UE checks for scheduling
messages (indicated by its C-RNTI on the PDCCH) during the 'On Duration' period of
either the long DRX cycle or the short DRX cycle depending on the currently active
cycle. When a scheduling message is received during an 'On Duration', the UE starts
an 'Inactivity Timer' and monitors the PDCCH in every subframe while the Inactivity
Timer is running. During this period, the UE can be regarded as being in a continuous
reception mode. Whenever a scheduling message is received while the Inactivity Timer
is running, the UE restarts the Inactivity Timer, and when it expires the UE moves
into a short DRX cycle and starts a 'Short DRX cycle timer'. The short DRX cycle may
also be initiated by means of a DRX MAC Control Element from the eNodeB, instructing
the UE to enter DRX. When the short DRX cycle timer expires, the UE moves into a long
DRX cycle. In addition to this DRX behavior, a 'HARQ Round Trip Time (RTT) timer'
is defined with the aim of allowing the UE to sleep during the HARQ RTT. When decoding
of a downlink transport block for one HARQ process fails, the UE can assume that the
next retransmission of the transport block will occur after at least 'HARQ RTT' subframes.
While the HARQ RTT timer is running, the UE does not need to monitor the PDCCH. At
the expiry of the HARQ RTT timer, the UE resumes reception of the PDCCH as normal.
[0080] Above mentioned DRX related timers like DRX-Inactivity timer, HARQ RTT timer, DRX
retransmission timer and Short DRX cycle timer are started and stopped by events such
as reception of a PDCCH grant or MAC Control element (DRX MAC CE); hence the DRX status
(active time or non-active time) of the UE can change from one subframe to another
and is hence not always predictable by the mobile station or eNodeB.
[0081] There is only one DRX cycle per UE. All aggregated component carriers follow this
DRX pattern.
Shortcomings of current periodic CSI/SRS reporting during DRX
[0082] As mentioned before, the DRX status (i.e. Active Time/non-Active Time) of a UE can
change from subframe to subframe. DRX-related timers (like DRX-Inactivity timer, HARQ
RTT timer, DRX retransmission timer) are started and stopped by various events, such
as reception of a PDCCH grant or of MAC control elements (DRX MAC CE), thus putting
the UE into Active Time or non-Active Time. The behavior of the UE for Active Time
and non-Active Time is clearly defined by the standard. Correspondingly, the UE shall
transmit periodic CSI reports and SRS only during the Active time. However, the UE
needs some time to process received signaling or information changing its DRX status,
and also need some time to prepare the CSI report and SRS. The processing time strongly
depends on the implementation of the UE. This however may lead to problems during
operation of the UE, as will be explained in detail below.
[0083] Assuming the UE is currently in Active Time and the DRX Inactivity timer is running,
if a UE receives in the last subframe before the DRX Inactivity timer expires (e.g.
subframe N) a PDCCH indicating a new transmission (UL or DL), the UE will also be
in Active Time in the next subframe, i.e. subframe N+1 and the DRX Inactivity timer
is restarted.
[0084] Due to the processing time in the UE, the UE may only now at the beginning/middle
of subframe N+1 that subframe N+1 is still Active Time. Assuming that the periodic
CSI report is configured to be transmitted in subframe N+1, the UE may not have time
to prepare the CSI report for transmission, since it initially assumed to enter DRX,
i.e. be in non-Active Time during subframe N+1, and thus to not be necessary to transmit
the CSI report. Consequently, the UE might not be able to transmit the periodic CSI
report in subframe N+1, contrary to the specification mandating the UE to transmit
periodic CSI on PUCCH during Active Time in the configured subframes.
[0085] In summary, the UE behavior with respect to CSI/SRS transmission cannot immediately
follow the DRX status of the UE, since the UE needs some time to become aware of the
signaling and to prepare the necessary uplink transmission accordingly. The time after
the Active Time has been suddenly started/prolonged or ended due to reception of respective
signaling from the network is generally referred to as "transient phase" or "uncertain
period". In order to account for the processing delay in the UE, an exception on the
periodic CSI transmission on PUCCH and periodic SRS transmission has been introduced
for LTE Rel-8/9/10 in TS 36.321, as follows.
A UE may optionally choose to not send CQI/PMI/RI/PTI reports on PUCCH and/or type-0-triggered
SRS transmissions for up to 4 subframes following a PDCCH indicating a new transmission
(UL or DL) received in subframe
n-i, where
n is the last subframe of Active Time and
i is an integer value from 0 to 3. After Active Time is stopped due to the reception
of a PDCCH or a MAC control element a UE may optionally choose to continue sending
CQI/PMI/RI/PTI reports on PUCCH and/or SRS transmissions for up to 4 subframes. The
choice not to send CQI/PMI/RI/PTI reports on PUCCH and/Or type-0-triggerred SRS transmissions
is not applicable for subframes where
onDurationTimer is running and is not applicable for subframes
n-i to n.
[0086] Despite the above exception, the eNB in general expects uplink transmissions from
the UE according to the specification. Thus, with respect to CSI/SRS reporting, when
the UE is in Active Time, the UE is expected to transmit periodic CSI reports on PUCCH
and SRS, depending on the periodicity of CSI/SRS. Correspondingly, the eNB does not
expect any periodic CSI/SRS transmission from UE in subframes where the UE is in non-Active
Time.
[0087] However, due to the UE behavior introduced to cover the "transient phases", the UE
behavior for these "transient phases" is not predictable for the eNB. Therefore, the
network must be able to correctly decode the PUCCH channel or the PUSCH channel for
cases, when it does not know if periodic CSI or SRS reports have been sent or not.
In other words, double decoding is necessary at the UE to cover both transmission
cases, i.e. with or without CSI/SRS. For instance:
- If CSI happens to coincide with a DL HARQ PUCCH transmission in the transient phase,
then, the network needs to perform double decoding to handle both the case, when CSI
has been sent and the case when CSI has not been sent.
- If SRS happens to coincide with a PUSCH transmission that is outside the configured
bandwidth of SRS in the transient phase, then the network needs to perform double
decoding to handle both the case when SRS has been sent and the case when SRS has
not been sent.
[0088] There are many more combinations of control information for which eNB needs to perform
double decoding for two different data transmissions formats in order to be able to
detect the control information correctly. Some of these combinations are given in
the table below, which is taken from R2-124687; it should be noted that the list is
not complete, but shall give an overview.
Case (possible collisions during transient phase) |
If CSI/SRS is transmitted |
If CSI/SRS is not transmitted |
Double decoding needed? |
CSI + Data |
Data (RMed) + CSI |
Data |
Yes |
CSI + AN |
CSI + AN (jointly coded) |
AN |
Yes |
CSI+SR |
SR (CSI dropped) |
SR |
No |
CSI + Data + SR |
Data (RMed) + CSI |
Data |
Yes |
CSI + Data + AN |
[CSI & Data Muxed] (RMed) + AN |
Data (RMed) + AN |
Yes |
CSI+AN+SR |
AN + SR |
AN+SR |
No |
CSI + Data + AN +SR |
[CSI & Data Muxed] (RMed) + AN |
Data (RMed) + AN |
Yes |
SRS + Data |
Data (RMed) + SRS |
Data |
Yes |
SRS+ AN |
[AN (shorten format) + SRS] or AN (normal format) |
AN (shorten format) or AN (normal format) |
No |
SRS+SR |
[SR (shorten format) + SRS] or SR (normal format) |
SR (shorten format) or SR (normal format) |
No |
SRS + Data + SR |
Data (RMed) + SRS |
Data |
Yes |
SRS+ Data + AN |
Data (RMed over AN/SRS) + AN + SRS |
Data (RMed over AN) + AN |
Yes |
SRS + AN + SR |
[AN + SR] (shorten format) + SRS or [AN + SR] (normal format) |
[AN + SR] (shorten format) or [AN + SR] (normal format) |
No |
SRS + Data + AN+SR |
Data (RMed over AN/SRS) + AN + SRS |
Data (RMed over AN) + AN |
Yes |
CSI + SRS + Data |
Data (RMed over CSI/SRS) + CSI + SRS |
Data (RMed over CSI) + CSI |
Yes |
CSI + SRS+ AN |
AN (shorten format) + SRS or AN (normal format) |
AN (shorten format) or AN (normal format) |
No |
CSI + SRS + SR |
SR (shorten format) + SRS |
SR (shorten format) |
No |
CSI + SRS+ Data + SR |
Data (RMed over CSI/SRS) + CSI + SRS |
Data (RMed over CSI) + CSI |
Yes |
CSI + SRS+ |
[CSI & Data Muxed] (RMed over |
Data (RMed over AN) + AN |
Yes |
Data + AN |
AN/SRS) + AN + SRS |
|
|
CSI + SRS + AN +SR |
AN + SR (shorten format) + SRS |
AN + SR (normal format) |
Yes |
CSI + SRS + Data + AN + SR |
[CSI & Data Muxed] (RMed over AN/SRS) + AN + SRS |
Data (RMed over AN) + AN |
Yes |
[0089] As can be seen, the double decoding caused by the transient phases might happen quite
often, and causes unnecessary complexity and computational cost within the network.
The decoding in the eNB relies on the uplink transmissions having a certain transmission
format, as for example Format 2, 2a and 2b always including a CSI. When the transmission
format changes due to the sudden transmission or non-transmission of the CSI, the
decoding in the eNB may fail due to the wrong transmission format, which in turn leads
to degradation of the throughput.
[0090] This applies in a similar manner for the transmission of the SRS. Provided the assigned
resource blocks for PUSCH are not overlapping with the cell-specific SRS frequency
region, in case the UE doesn't transmit SRS in this subframe, the UE uses the last
SC-FDMA symbol in the subframe for PUSCH. In case the UE transmit SRS in this subframe,
the UE does not use the last SC-FDMA symbol for PUSCH. Therefore, depending on whether
UE is transmitting SRS (which is dependent on the DRX status of the subframe), the
number of SC-FDMA symbols for PUSCH changes, which in turn means that eNB would have
to check two different PUSCH symbol usages in those subframes. However, this uncertainty
can be easily avoided by the eNB by assigning only PUSCH resources to the UE which
lie within the cell-specific SRS region, which is majority of the assignment; in this
case the UE will never map PUSCH on the last SC-FDMA symbol in a subframe where periodic
SRS has been configured. Nevertheless, the problem remains for the case where the
assigned resource blocks for the PUSCH do not lie within the cell-specific SRS region.
SUMMARY OF THE INVENTION
[0091] One object of the invention is to provide a deterministic UE behavior for transmitting
CSI and/or SRS, that solves the problems of the prior art as discussed above.
[0092] The object is solved by the subject matter of the independent claims. Advantageous
embodiments are subject to the dependent claims.
[0093] The present invention provides a method of a first embodiment for transmitting a
channel quality information report and/or a sounding reference symbol from a mobile
station to a base station in a mobile communication system in subframe N. Subframe
N is configured for the mobile station for transmission of periodic channel quality
information reports and/or periodic sounding reference symbols. It is determined whether
the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N,
at least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, received by the mobile station until and including
subframe N-4 only, and
DRX-related timers running for the mobile station, including at least one of a DRX
Inactivity Timer, a DRX OnDuration Timer and a DRX Retransmission Timer.
[0094] The mobile station transmits the channel quality information report and/or the sounding
reference symbol to the base station in subframe N, in case the mobile station is
determined to be in DRX Active Time in subframe N.
[0095] According to an advantageous variant of the first embodiment of the invention which
can be used in addition or alternatively to the above, the base station performs the
steps of:
determining whether the mobile station will be in DRX Active Time or DRX Non-Active
Time in subframe N, at least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, transmitted to the mobile station until and including
subframe N-4 only, and
DRX-related timers running for the mobile station, including at least one of a DRX
Inactivity Timer, a DRX OnDuration Timer and a DRX Retransmission Timer,
receiving the channel quality information report and/or the sounding reference symbol
from the mobile station in subframe N, in case the mobile station is determined by
the determining step to be in DRX Active Time in subframe N.
[0096] According to an advantageous variant of the first embodiment of the invention which
can be used in addition or alternatively to the above, the determining is further
based on MAC control elements, relating to the DRX operation, received by the mobile
station until and including subframe N-(4+k) only, where k is an integer value from
1 to K. Alternatively, the determining is further based on MAC control elements, relating
to the DRX operation, for which an acknowledgment is transmitted by the mobile station
until and including subframe N-(3+k) only, where k is an integer value from 1 to K.According
to an advantageous variant of the first embodiment of the invention which can be used
in addition or alternatively to the above, the DRX-related timers are considered in
the determining based on uplink resource grants for the uplink shared channel and/or
downlink resource assignments for the downlink shared channel, received by the mobile
station until and including subframe N-4 only, and further based on the value of the
DRX-related timers at subframe N-4.
[0097] The present invention provides a mobile station of a first embodiment for transmitting
a channel quality information report and/or a sounding reference symbol to a base
station in a mobile communication system in subframe N. Subframe N is configured for
the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A processor of the mobile station determines
whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe
N, at least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, received by the mobile station until and including
subframe N-4 only, and
DRX-related timers running for the mobile station, including at least one of a DRX
Inactivity Timer, a DRX OnDuration Timer and a DRX Retransmission Timer.
[0098] A transmitter of the mobile station transmits the channel quality information report
and/or the sounding reference symbol to the base station in subframe N, in case the
mobile station is determined by the processor to be in DRX Active Time in subframe
N.
[0099] According to an advantageous variant of the mobile station of the first embodiment
of the invention which can be used in addition or alternatively to the above, the
processor performs the determining further based on MAC control elements, relating
to the DRX operation, received by the mobile station until and including subframe
N-(4+k) only, where k is an integer value from 1 to K. Alternatively, the processor
performs the determining further based on MAC control elements, relating to the DRX
operation, for which an acknowledgment is transmitted by the mobile station until
and including subframe N-(3+k) only, where k is an integer value from 1 to K. The
present invention provides a base station of a first embodiment for receiving a channel
quality information report and/or a sounding reference symbol from a mobile station
a mobile communication system in subframe N. Subframe N is configured for the mobile
station for transmission of periodic channel quality information reports and/or periodic
sounding reference symbols. A processor of the base station determines whether the
mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N, at
least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, transmitted to the mobile station until and including
subframe N-4 only, and
DRX-related timers running for the mobile station, including at least one of a DRX
Inactivity Timer, a DRX OnDuration Timer and a DRX Retransmission Timer,
[0100] A receiver of the base station receives the channel quality information report and/or
the sounding reference symbol from the mobile station in subframe N, in case the mobile
station is determined by the processor to be in DRX Active Time in subframe N.
[0101] The present invention provides a method of a second embodiment for transmitting a
channel quality information report and/or a sounding reference symbol from a mobile
station to a base station in a mobile communication system in subframe N. Subframe
N is configured for the mobile station for transmission of periodic channel quality
information reports and/or periodic sounding reference symbols. It is determined whether
the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N,
at least based on MAC control elements, relating to the DRX operation, received by
the mobile station until and including subframe N-(4+k) only, where k is an integer
value from 1 to K. The mobile station transmits the channel quality information report
and/or the sounding reference symbol to the base station in subframe N, in case the
mobile station is determined by the determining step to be in DRX Active Time in subframe
N.According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, the base station
determines whether the mobile station will be in DRX Active Time or DRX Non-Active
Time in subframe N, at least based on MAC control elements, relating to the DRX operation,
transmitted to the mobile station until and including subframe N-(4+k) only, where
k is an integer value from 1 to K, and based on feedback received from the mobile
station relating to the decoding success for the MAC control elements. The base station
receives the channel quality information report and/or the sounding reference symbol
from the mobile station in subframe N, in case the mobile station is determined by
the determining to be in DRX Active Time in subframe N.
[0102] According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, the determining
disregards any MAC control elements, relating to the DRX operation, destined for the
mobile station in subframes N-(3+k) to N.
[0103] According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, the mobile
station does not transmit the channel quality information report and/or the sounding
reference symbol to the base station in subframe N, in case the mobile station is
determined by the determining step to be in DRX Non-Active Time in subframe N.
[0104] According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, the determining
is further based on uplink resource grants for the uplink shared channel and/or downlink
resource assignments for the downlink shared channel, received by the mobile station
until and including subframe N-4 only. Alternatively, the determining is further based
on uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, received by the mobile station until and including
subframe N-(4+k) only.
[0105] According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, the determining
is further based on DRX-related timers running for the mobile station, including at
least one of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRX Retransmission
Timer.
[0106] According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, the determining
comprises the step of estimating the state of the DRX-related timers at subframe N
based on uplink resource grants for the uplink shared channel and/or downlink resource
assignments for the downlink shared channel, received by the mobile station until
and including subframe N-4 only, and further based on the value of the DRX-related
timers at subframe N-4.
[0107] According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, the mobile
station transmits an acknowledgment or non-acknowledgment in subframe N-k for the
MAC control element, relating to the DRX operation, received by the mobile station
in subframe N-(4+k). The mobile station tramsmits an acknowledgment or non-acknowledgment
in subframe N for a MAC control element, relating to the DRX operation, received by
the mobile station in subframe N-4.
[0108] According to an advantageous variant of the method of the second embodiment of the
invention which can be used in addition or alternatively to the above, processing
of the determining step is started in the mobile station at subframe N-(4+k), and
after finishing the process of the determining step, preparing by the mobile station
the channel quality report and/or the sounding reference symbol for transmission in
subframe N for the transmission step.
[0109] The present invention provides a mobile station of the second embodiment for transmitting
a channel quality information report and/or a sounding reference symbol to a base
station in a mobile communication system in subframe N. Subframe N is configured for
the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A processor of the mobile station determines
whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe
N, at least based on MAC control elements, relating to the DRX operation, received
by the mobile station until and including subframe N-(4+k) only, where k is an integer
value from 1 to K. A transmitter of the mobile station transmits the channel quality
information report and/or the sounding reference symbol to the base station in subframe
N, in case the mobile station is determined by the processor to be in DRX Active Time
in subframe N.
[0110] According to an advantageous variant of the mobile station of the second embodiment
of the invention which can be used in addition or alternatively to the above, the
processor disregards any MAC control elements, relating to the DRX operation, destined
for the mobile station in subframes N-(3+k) to N.
[0111] According to an advantageous variant of the mobile station of the second embodiment
of the invention which can be used in addition or alternatively to the above, the
processor performs the determining further based on uplink resource grants for the
uplink shared channel and/or downlink resource assignments for the downlink shared
channel, received by the mobile station until and including subframe N-4 only. Alternatively,
the processor performs the determining further based on the uplink resource grants
for the uplink shared channel and/or downlink resource assignments for the downlink
shared channel, received by the mobile station until and including subframe N-(4+k)
only.
[0112] According to an advantageous variant of the mobile station of the second embodiment
of the invention which can be used in addition or alternatively to the above, the
processor performs the determining further based on DRX-related timers running for
the mobile station, including at least one of a DRX Inactivity Timer, a DRX OnDuration
Timer and a DRX Retransmission Timer.
[0113] According to an advantageous variant of the mobile station of the second embodiment
of the invention which can be used in addition or alternatively to the above, the
processor performs the determining comprising the step of estimating the state of
the DRX-related timers at subframe N based on uplink resource grants for the uplink
shared channel and/or downlink resource assignments for the downlink shared channel,
received by the mobile station until and including subframe N-4 only, and further
based on the value of the DRX-related timers at subframe N-4.
[0114] The present invention provides a base station of the second embodiment for receiving
a channel quality information report and/or a sounding reference symbol from a mobile
station a mobile communication system in subframe N. Subframe N is configured for
the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A processor of the base station determines
whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe
N, at least based on MAC control elements, relating to the DRX operation, transmitted
to the mobile station until and including subframe N-(4+k) only, where k is an integer
value from 1 to K, and based on feedback received from the mobile station relating
to the decoding success for the transmitted MAC control elements. A receiver of the
base station receives the channel quality information report and/or the sounding reference
symbol from the mobile station in subframe N, in case the mobile station is determined
by the processor to be in DRX Active Time in subframe N.
[0115] The present invention provides a method of a third embodiment for transmitting a
channel quality information report and/or a sounding reference symbol from a mobile
station to a base station in a mobile communication system in subframe N. Subframe
N is configured for the mobile station for transmission of periodic channel quality
information reports and/or periodic sounding reference symbols. It is determined whether
the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N,
at least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, received by the mobile station until and including
subframe N-(4+k) only, where k is an integer value from 1 to K, and
MAC control elements, relating to the DRX operation, received by the mobile station
until and including subframe N-(4+k) only, where k is an integer value from 1 to K.
[0116] The mobile station transmits the channel quality information report and/or the sounding
reference symbol to the base station in subframe N, in case the mobile station is
determined by the determining to be in DRX Active Time in subframe N.
[0117] According to an advantageous variant of the method of the third embodiment of the
invention which can be used in addition or alternatively to the above, the base station
determines whether the mobile station will be in DRX Active Time or DRX Non-Active
Time in subframe N, at least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, transmitted to the mobile station until and including
subframe N-(4+k) only, where k is an integer value from 1 to K, and
MAC control elements, relating to the DRX operation, transmitted to the mobile station
until and including subframe N-(4+k) only, where k is an integer value from 1 to K,
[0118] The base station receives the channel quality information report and/or the sounding
reference symbol from the mobile station in subframe N, in case the mobile station
is determined by the determining step to be in DRX Active Time in subframe N.
[0119] According to an advantageous variant of the method of the third embodiment of the
invention which can be used in addition or alternatively to the above, the determining
is further based on DRX-related timers running for the mobile station, including at
least one of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRX Retransmission
Timer. Preferably the determining then comprises estimating the state of the DRX-related
timers at subframe N based on uplink resource grants for the uplink shared channel
and/or downlink resource assignments for the downlink shared channel, received by
the mobile station until and including subframe N-4 only, and further based on the
value of the DRX-related timers at subframe N-4.
[0120] The present invention provides a mobile station of the third embodiment for transmitting
a channel quality information report and/or a sounding reference symbol to a base
station in a mobile communication system in subframe N. Subframe N is configured for
the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A processor of the mobile station determines
whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe
N, at least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, received by the mobile station until and including
subframe N-(4+k) only, where k is an integer value from 1 to K, and
MAC control elements, relating to the DRX operation, received by the mobile station
until and including subframe N-(4+k) only, where k is an integer value from 1 to K,
[0121] A transmitter of the mobile station transmits the channel quality information report
and/or the sounding reference symbol to the base station in subframe N, in case the
mobile station is determined by the processor to be in DRX Active Time in subframe
N.
[0122] According to an advantageous variant of the mobile station of the third embodiment
of the invention which can be used in addition or alternatively to the above, the
processor performs the determining further based on DRX-related timers running for
the mobile station, including at least one of a DRX Inactivity Timer, a DRX OnDuration
Timer and a DRX Retransmission Timer.
[0123] The present invention also provides a base station of the third embodiment for receiving
a channel quality information report and/or a sounding reference symbol from a mobile
station a mobile communication system in subframe N. Subframe N is configured for
the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A processor of the base station determines
whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe
N, at least based on:
uplink resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, transmitted to the mobile station until and including
subframe N-(4+k) only, where k is an integer value from 1 to K, and
MAC control elements, relating to the DRX operation, transmitted to the mobile station
until and including subframe N-(4+k) only, where k is an integer value from 1 to K.
[0124] A receiver of the base station receives the channel quality information report and/or
the sounding reference symbol from the mobile station in subframe N, in case the mobile
station is determined by the determining step to be in DRX Active Time in subframe
N.
[0125] The present invention further provides a method of a fourth embodiment for transmitting
a channel quality information report and/or a sounding reference symbol from a mobile
station to a base station in a mobile communication system in subframe N. Subframe
N is configured for the mobile station for transmission of periodic channel quality
information reports and/or periodic sounding reference symbols. It is determined whether
the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe N,
at least based on MAC control elements, relating to the DRX operation, for which an
acknowledgment is transmitted by the mobile station until and including subframe N-(3+k),
where k is an integer value from 1 to K. The mobile station transmits the channel
quality information report and/or the sounding reference symbol to the base station
in subframe N, in case the mobile station is determined by the determining to be in
DRX Active Time in subframe N.
[0126] According to an advantageous variant of the method of the fourth embodiment of the
invention which can be used in addition or alternatively to the above, the base station
determines whether the mobile station will be in DRX Active Time or DRX Non-Active
Time in subframe N, at least based on MAC control elements, relating to the DRX operation,
for which an acknowledgment is received from the mobile station until and including
subframe N-(3+k), where k is an integer value from 1 to K. The base station receives
the channel quality information report and/or the sounding reference symbol from the
mobile station in subframe N, in case the mobile station is determined by the determining
step to be in DRX Active Time in subframe N.
[0127] According to an advantageous variant of the method of the fourth embodiment of the
invention which can be used in addition or alternatively to the above, the determining
is further based on DRX-related timers running for the mobile station, including at
least one of a DRX Inactivity Timer, a DRX OnDuration Timer and a DRX Retransmission
Timer. Preferably this may be done by estimating the state of the DRX-related timers
at subframe N based on uplink resource grants for the uplink shared channel and/or
downlink resource assignments for the downlink shared channel, received by the mobile
station until and including subframe N-4 only, and further based on the value of the
DRX-related timers at subframe N-4
[0128] According to an advantageous variant of the method of the fourth embodiment of the
invention which can be used in addition or alternatively to the above, the determining
disregards any MAC control elements, relating to the DRX operation, for which an acknowledgement
is transmitted by the mobile station in subframes N-(2+k) to N.
[0129] According to an advantageous variant of the method of the fourth embodiment of the
invention which can be used in addition or alternatively to the above, the determining
is further based on uplink resource grants for the uplink shared channel and/or downlink
resource assignments for the downlink shared channel, received by the mobile station
until and including subframe N-4 only.
[0130] The present invention further provides a mobile station of the fourth embodiment
for transmitting a channel quality information report and/or a sounding reference
symbol to a base station in a mobile communication system in subframe N. Subframe
N is configured for the mobile station for transmission of periodic channel quality
information reports and/or periodic sounding reference symbols. A processor of the
mobile station determines whether the mobile station will be in DRX Active Time or
DRX Non-Active Time in subframe N, at least based on MAC control elements, relating
to the DRX operation, for which an acknowledgment is transmitted by the mobile station
until and including subframe N-(3+k), where k is an integer value from 1 to K. A transmitter
of the mobile station transmits the channel quality information report and/or the
sounding reference symbol to the base station in subframe N, in case the mobile station
is determined by the processor to be in DRX Active Time in subframe N.
[0131] According to an advantageous variant of the mobile station of the fourth embodiment
of the invention which can be used in addition or alternatively to the above, the
processor performs the determining further based on DRX-related timers running for
the mobile station, including at least one of a DRX Inactivity Timer, a DRX OnDuration
Timer and a DRX Retransmission Timer. Alternatively, the processor performs the determining
further based on uplink resource grants for the uplink shared channel and/or downlink
resource assignments for the downlink shared channel, received by the mobile station
until and including subframe N-4 only.
[0132] According to an advantageous variant of the mobile station of the fourth embodiment
of the invention which can be used in addition or alternatively to the above, the
processor performs the determining by disregarding any MAC control elements, relating
to the DRX operation, for which an acknowledgement is transmitted by the mobile station
in subframes N-(2+k) to N.
[0133] The present invention further provides a base station of the fourth embodiment for
receiving a channel quality information report and/or a sounding reference symbol
from a mobile station a mobile communication system in subframe N. Subframe N is configured
for the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A processor of the base station determines
whether the mobile station will be in DRX Active Time or DRX Non-Active Time in subframe
N, at least based on MAC control elements, relating to the DRX operation, for which
an acknowledgment is received from the mobile station until and including subframe
N-(3+k), where k is an integer value from 1 to K. A receiver of the base station receives
the channel quality information report and/or the sounding reference symbol from the
mobile station in subframe N, in case the mobile station is determined by the determining
step to be in DRX Active Time in subframe N.
[0134] The present invention further provides a method of a fifth embodiment for transmitting
a channel quality information report and/or a sounding reference symbol from a mobile
station to a base station in a mobile communication system, in subframe N. Subframe
N is configured for the mobile station for transmission of periodic channel quality
information reports and/or periodic sounding reference symbols. The mobile station
transmits the channel quality information report and/or the sounding reference symbol
to the base station in subframe N, in case the mobile station is in DRX Active Time
in subframe N-k, where k is an integer value from 1 to K.
[0135] The present invention further provides a mobile station of the fifth embodiment for
transmitting a channel quality information report and/or a sounding reference symbol
to a base station in a mobile communication system in subframe N. Subframe N is configured
for the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A transmitter of the mobile station transmits
the channel quality information report and/or the sounding reference symbol to the
base station in subframe N, in case the mobile station is in DRX Active Time in subframe
N-k, where k is an integer value from 1 to K.
[0136] The present invention further provides a base station of the fifth embodiment for
receiving a channel quality information report and/or a sounding reference symbol
from a mobile station a mobile communication system in subframe N. Subframe N is configured
for the mobile station for transmission of periodic channel quality information reports
and/or periodic sounding reference symbols. A receiver of the base station receiveds
the channel quality information report and/or the sounding reference symbol to the
base station in subframe N, in case the mobile station is in DRX Active Time in subframe
N-k, where k is an integer value from 1 to K.
Brief description of the Figures
[0137] In the following the invention is described in more detail with reference to the
attached figures and drawings.
- Fig. 1
- shows an exemplary architecture of a 3GPP LTE system,
- Fig. 2
- shows an exemplary overview of the overall E-UTRAN architecture of 3GPP LTE,
- Fig. 3
- shows exemplary subframe boundaries on a downlink component carrier as defined for
3GPP LTE (Release 8/9),
- Fig. 4
- shows an exemplary downlink resource grid of a downlink slot as defined for 3GPP LTE
(Release 8/9),
- Fig. 5 & 6
- show the 3GPP LTE-A (Release 10) Layer 2 structure with activated carrier aggregation
for the downlink and uplink, respectively,
- Fig. 7
- shows a state diagram for a mobile terminal and in particular the states RRC_CONNECTED
and RRC_IDLE and the functions to be performed by the mobile terminal in these states,
- Fig. 8
- illustrates the DRX operation of a mobile terminal, and in particular the DRX opportunity,
on-duration, according to the short and long DRX cycle,
- Fig. 9 to 12
- are subframe diagrams illustrating the mobile terminal and base station operation
for the first embodiment of the invention, for different scenarios depending on the
subframe at which a PDCCH is received,
- Fig. 13 and 14
- are subframe diagrams illustrating the mobile terminal and base station operation
and a remaining problem of ambiguousness,
- Fig. 15 and 16
- are subframe diagrams illustrating the mobile terminal and base station operation
for the second embodiment of the invention,
- Fig. 17 to 19
- are subframe diagrams illustrating the mobile terminal and base station operation
for the fourth embodiment of the invention, and
- Fig. 20
- is a subframe diagram illustrating the mobile terminal and base station operation
for the fifth embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0138] The following paragraphs will describe various embodiments of the invention. For
exemplary purposes only, most of the embodiments are outlined in relation to a radio
access scheme according to 3GPP LTE (Release 8/9) and LTE-A (Release 10/11) mobile
communication systems, partly discussed in the Technical Background section above.
It should be noted that the invention may be advantageously used for example in a
mobile communication system such as 3GPP LTE-A (Release 10/11/12) communication systems
as described in the Technical Background section above, but the invention is not limited
to its use in this particular exemplary communication networks.
[0139] The term
"DRX status" used in the claims and also throughout the description refers to the mobile station
being either in
"DRX Active Time" or in
"DRX Non-Active Time". The
"DRX Active Time" mainly denotes the time during which the mobile station is monitoring the PDCCH and
performs others tasks such as transmission of periodic SRS and/or periodic CSI, as
configured. The
"DRX Non-Active Time" mainly denotes the time during which the mobile station does not monitor the PDCCH
and does not transmit the periodic SRS and/or periodic CSI.
[0140] The expression
"until and including subframe N-4 only", and similar expressions for N-(4+k) etc, used in the claims and also throughout the
description, shall limit the subframes which are to be considered for the determination.
The expression correspondingly refers to only those subframes N-4, N-5, N-6, N-7,
N-8, N-9 etc.. Correspondingly, subframes N-3, N-2, N-1 and current subframe N are
not to be included according to the expression and thus are disregarded (discarded),
i.e. not considered, for the determination. Another equivalent expression is "only
subframes before subframe N-3".
[0141] The expression
"at subframe N-4", and similar expressions referring to other subframe indices, used in the description,
should not be necessarily understood as meaning that the process (e.g. estimating)
is to be performed completely in said indicated subframe, but rather that the process
is started in said indicated subframe, and may well proceed to subsequent subframes
if the processing as such needs more time to be terminated. This of course partly
depends on the implementation of the mobile station or base station executing said
process.
[0142] In the following, several embodiments of the invention will be explained in detail.
The explanations should not be understood as limiting the invention, but as a mere
example of the invention's embodiments to better understand the invention. A skilled
person should be aware that the general principles of the invention as laid out in
the claims can be applied to different scenarios and in ways that are not explicitly
described herein. Correspondingly, the following scenarios assumed for explanatory
purposes of the various embodiments shall not limit the invention as such.
[0143] One main aspect of the invention is to make the determination of whether or not to
transmit the CSI/SRS deterministic, i.e. where the result of the determination may
be determined in advance; or put differently, no randomness is involved.
[0144] For the following embodiments of the invention, it is assumed that subframe N is
configured for periodic CSI/SRS reporting. For ease of explanation, it is assumed
that periodic CSI and periodic SRS are configured for the same subframe (i.e. subframe
N); however, this is not necessarily always the case. The embodiments of the invention
may well be applied to cases where the periodic CSI and SRS are configured for different
subframes, in which case the embodiments of the invention are to be applied separately
for CSI and SRS.
[0145] Furthermore, the Figures discussed below to explain the various embodiments of the
invention assume the ideal situation where the processing time at the UE/eNodeB is
negligible and not taken into account for illustration purposes. Of course, in real
world implementation the UEs and eNodeB need a certain processing time (e.g. several
subframes) to properly decode a downlink transmission and process the decoded information
accordingly. For example, after receiving a DRX MAC CE instruction to enter DRX, the
UE is supposed to immediately enter DRX mode in the next subframe according to the
standard; however, this will not be possible in reality, since the UE will need time
to process the DRX MAC CE and may actually only enter DRX with a e.g. 2 subframe delay.
First embodiment
[0146] According to a first set of embodiments of the invention, instead of acting according
to the DRX status at the time of the actual uplink transmission, the UE estimates
at subframe N-4 the DRX status of a subframe which is 4 subframes ahead (i.e. subframe
N) and decides based on the estimated status whether to transmit the periodic CSI/SRS
or not. For the estimation, the UE considers all PDCCHs (i.e. uplink resource grants
and/or downlink resource assignments) which are received up to subframe N-4 (having
possible influence on the DRX status of UE for subframe N), but does not consider
any PDCCHs received after subframe N-4, i.e. at subframes N-3, N-2, N-1 and N. The
reason why UE looks 4 subframes ahead, is that this corresponds to the same timing
requirements as defined in the above-cited exception on the periodic CSI transmission
on PUCCH and periodic SRS transmission introduced for LTE Rel-8/9/10 in TS 36.321.
[0147] Furthermore, the estimation is not only based on the UL grants/DL assignments as
just mentioned but is also based on at least one of DRX-related timer(s) running for
the mobile station at the time of subframe N, such as the Inactivity Timer, the OnDuration
Timer, and/or the Retransmission Timer. The DRX timers usually have a direct influence
on the DRX status of a subframe; i.e. whether or not the UE is in Active Time at subframe
N. Not all timers may be running at the same time. Furthermore, not all of the DRX
timers configured for the mobile station must be indeed considered; only a subset
(e.g. one DRX timer) of the DRX timers could be taken into account. For example, it
would be possible to just consider the OnDuration timer, but not the Retransmission
Timer, even if same is currently running when performing the determination as to whether
or not to transmit the CSI/SRS.
[0148] In particular, the UE estimates the values and status of the DRX timer(s) at subframe
N and thus foresees whether it will be in Active Time or not in subframe N depending
on the estimated DRX timer status/value at subframe N. Preferably of course, only
those DRX-related timers should be considered whose value at subframe N may be extrapolated
already at subframe N-4.
[0149] Again however, UE considers only those DRX timers whose value at subframe N are known
already at subframe N-4, e.g. UE knows already at subframe N-4 based on grants/assignments
received until and including subframe N-4 that OnDuration timer/DRX retransmission
timer is running at subframe N; in case a DRX timer value is reset or the DRX timer
is aborted due to the reception of a PDCCH, DRX MAC CE or a retransmission after subframe
N-4 (i.e. in subframes N-3, N-2, N-1, N), this is not considered for the estimation.
Correspondingly, the estimation considering the DRX-related timers is based on uplink
resource grants for the uplink shared channel and/or downlink resource assignments
for the downlink shared channel, received by the UE until and including subframe N-4
only, and further based on the estimation of status/values of the DRX-related timers
at subframe N.
[0150] By additionally considering the DRX-related timer(s) the accuracy of the estimation
of whether subframe N is Active Time or Non-Active Time for the mobile station, is
increased and hence the usefulness of CSI/SRS is increased.
[0151] In general, the UE shall transmit CSI/SRS to the eNodeB in case the subframe N is
estimated to be DRX Active, i.e. that the UE is in Active Time, based on the information
explained above. On the other hand, the UE shall not transmit CSI/SRS to the eNodeB
in case the subframe N is estimated to be DRX Non-Active, i.e. that the UE is in Non-Active
Time, based on the information explained above. In both cases, the transmission of
the CSI/SRS is depending on the estimation result for the DRX status, but is independent
from the actual DRX status of the UE at subframe N; the latter one may differ from
the estimated DRX status of the UE at subframe N. Correspondingly, the UE might have
to transmit CSI/SRS even though the UE is in Non-Active Time at subframe N; or conversely,
the UE does not transmit CSI/SRS even though the UE is in Active Time at subframe
N.
[0152] The estimation of the subframe N status beforehand as explained above is performed
at the eNodeB too. Thus, the eNodeB, having the same information as the UE with respect
to the estimation, will get to the same result of the estimation, and thus knows whether
the UE will transmit the CSI/SRS or not in subframe N. Accordingly, the eNodeB will
expect the transmission of CSI/SRS by the UE at subframe N and will receive the CSI/SRS
accordingly, in case of a positive estimation result, or will not expect and not try
to receive the CSI/SRS in case of a negative estimation result. No double decoding
at the eNodeB is necessary anymore, which leads to less eNodeB complexity. The estimation
as explained is deterministic and thus leads to foreseeable results of the estimation
for both the eNodeB and the UE.
[0153] Furthermore, this procedure basically provides the UE with 4 subframes for detecting
the reception of the PDCCH and the preparing of the CSI/SRS transmission.
[0154] The above explanation will become clear in connection with the following Fig. 9-12.
[0155] Fig. 9 and 10 illustrate the DRX operation of a mobile station and a base station
for the transmission or non-transmission of CSI/SRS depending on the result of the
estimation as will be explained. As apparent, it is assumed that the UE is in Active
Time, the DRX Inactivity Timer is running and would expire in subframe N-2, provided
no PDDCH is received before. A PDCCH (be it an uplink grant or a downlink assignment)
is received in subframe N-3, and subframes N-10 and N are configured for periodic
CSI/SRS transmission. Correspondingly, the UE reports CSI/SRS in subframe N-10 (not
considered for explanation) and now needs to decide whether to report CSI/SRS in subframe
N or not.
[0156] The UE as well as the eNodeB now determine whether or not the UE shall transmit CSI/SRS
as configured in subframe N or not. Correspondingly, the determination is based on
whether subframe N is determined to be Active or Non-Active for the UE. Put differently,
information, relating to the DRX status of a subframe, available until and including
subframe N-4 is considered for the determination, while information, available after
subframe N-4 is discarded for the determination (but still processed accordingly for
other processes).
[0157] Therefore, in Fig. 9 the PDCCH is received in subframe N-3, i.e. after subframe N-4,
and thus discarded for the determination as to whether or not the UE shall transmit
CSI/SRS in subframe N. On the other hand, the PDCCH of subframe N-3 is considered
as such for restarting the DRX-Inactivity Timer according to usual UE behavior, which
thus leads to the case that the UE remains in Active Time.
[0158] However, for the determination of whether to transmit or not the CSI/SRS, the UE
and the eNodeB determine that the UE would be in Non-Active Time in subframe N (in
contrast to the actual situation), for the following reason: until and including subframe
N-4 no PDCCH was received to restart the DRX Inactivity Timer; thus, the UE and eNodeB
determine, based on the current value of the DRX Inactivity Timer at subframe N-4,
that the DRX Inactivity Timer will indeed expire in subframe N-2. Due to the assumed
expiry of the DRX Inactivity Timer, the UE and the eNodeB determine that the UE will
be in Non-Active Time in subframe N (which is not true, due to the not considered
PDCCH in subframe N-3), and the UE will thus not transmit CSI/SRS contrary to the
configuration (see Fig. 9, "No UL transmission"). The eNodeB will not expect any transmission
of CSI/SRS from the UE and thus will not even try to receive CSI/SRS.
[0159] The exemplary scenario of Fig. 10 is quite similar to the one presented in Fig. 9,
with the important exception that the PDCCH is received in subframe N-4 instead of
in subframe N-3. Consequently, the determination as to whether to transmit or not
the CSI/SRS at the configured subframe N, in this case also considers the PDCCH at
subframe N-4. The DRX-Inactivity Timer is restarted in subframe N-4, due to the received
PDCCH. The estimation process estimates the DRX status of the UE for subframe N to
be Active Time (assuming that DRX-Inactivity Timer will not have expired at subframe
N), which means that the UE shall report CSI/SRS as configured. The eNodeB reaches
the same conclusion based on the same information, and thus expects the CSI/SRS reporting
from the UE. No double decoding at the eNodeB is necessary anymore, since the eNB
and UE reach the same unambiguous estimation result.
[0160] In Fig. 11 a different DRX scenario is presented, based on which the above-described
first embodiment will be explained further. It is assumed that the UE is in DRX mode,
in particular in the Short-DRX cycle, where OnDuration periods (Active Time) are alternated
with DRX Opportunities (Non-Active Periods). In this example, the OnDuration is taken
as three subframes long, with the Short-DRX cycle being 7 subframes long; the Non-Active
Time is thus 4 subframes. Again, subframes N-10 and N are considered to be configured
for periodic CSI/SRS reporting. The OnDuration Timer is running at the mobile station.
[0161] Since the above-explained embodiment also considers the DRX-related timers at the
UE, the UE and the eNB can estimate at subframe N-4, considering grants/assignments
received until and including subframe N-4, that the UE will be in Active Time in subframe
N, i.e. OnDuration timer is running. By taking the Short-DRX cycle timer and the OnDuration
Timer into account for the estimation, the UE as well as the eNB can exactly estimate
when the UE will be in Active Time and Non-Active Time. Again, the UE and the eNodeB
consider UL grants/DL assignments received up to and including subframe N-4 only,
which in this case however means that no PDCCHs are considered since no PDCCHs are
received recently. This in first instance means that the UE still remains in DRX mode,
alternating Active Times with Non-Active Times. When only considering the UL grants/DL
assignments, the UE/eNodeB would estimate that the UE is in Non-Active Time in subframe
N, since no PDCCH was received in time (up to and including subframe N-4) to "wake
up" the UE. However, by additionally considering the DRX-related timers at the subframe
N-4 (in particular the value of the Short-DRX cycle timer and the OnDuration timer),
it is foreseeable that the UE will be in Active Time in subframe N and thus shall
report the CSI/SRS. Both the UE and the eNodeB come to the same determination result,
and thus the UE transmits the CSI report and the SRS, and the eNodeB expects the CSI/SRS
without the need of double decoding.
[0162] A similar scenario of the DRX operation is explained in connection with Fig. 12,
where however, the OnDuration is only 2 subframes and the DRX opportunity is 5 subframes
long. As apparent from Fig. 12, in subframes N-2 and N-1 the UE would be in Active
Time of the OnDuration. In subframe N-2 the UE is supposed to receive a PDCCH (be
it a UL grant or DL assignment). In any case, the UE ideally wakes up as of the reception
of the PDCCH, i.e. as of subframe N-1 and starts the DRX-Inactivity Timer in subframe
N-2. The UE is thus in Active Time in subframe N (assuming DRX-Inactivity Timer does
not expire before subframe N) and should report the CSI/SRS as configured. This case
is one example where the DRX reporting would fall into the transient phase after the
reception of a PDCCH, where the eNodeB needs to perform double decoding to determine
whether CSI/SRS is actually transmitted or not.
[0163] According to the present embodiment however, it is possible to arrive at a foreseeable
behavior of the UE which avoids the need of double decoding at the eNodeB. According
to the present embodiment, only UL grant and DL assignments are considered that are
received until and including subframe N-4 for determining whether or not to transmit
the periodic CSI/SRS as configured. The PDCCH is received at subframe N-2 and accordingly
discarded for the estimation, which in combination with the DRX-related timer values/status
leads to the estimation result that the UE is in Non-Active Time in subframe N, and
thus the UE shall not transmit CSI/SRS to the eNodeB. Correspondingly, the UE does
not transmit CSI/SRS although it is in Active Time at subframe N, due to the received
PDCCH in subframe N-2.
[0164] Therefore, additionally considering DRX-related timers is beneficial and depending
on the circumstance may lead to a different estimation result than without considering
DRX-related timers. Although for the above-explained scenarios only some of the DRX-related
were considered, the embodiment of the invention allows considering any or any combination
of the DRX-related timers, also depending on which DRX timers are currently running,
such as the DRX-retransmission timer or the Long-DRX cycle timer. Thus, the embodiment
of the invention shall not be restricted to merely the above-explained exemplary scenarios.
[0165] The reason why the consideration of OnDuration timer is appealing for the determination
whether to send CSI/SRS or not is that the mobile can know beforehand when OnDuration
timer is running based on the formula given in section 5.7 of TS36.321.
- If the Short DRX Cycle is used and [(SFN * 10) + subframe number] modulo (shortDRX-Cycle) = (drxStartOffset) modulo (shortDRX-Cycle); or
- if the Long DRX Cycle is used and [(SFN * 10) + subframe number] modulo (longDRX-Cycle) = drxStartOffset:
- start onDurationTimer.
[0166] As can be seen from the formula, the subframes where OnDuration timer is running
can be unambiguously determined by the mobile station and the eNodeB for the different
DRX cycles. However, whether DRX Short Cycle or DRX Long Cycle is used in a specific
subframe depends on other factors like DRX-Inactivity timer status and correspondingly
PDCCH reception status. Therefore, according to the above mentioned embodiment, UE
will consider the grants/assignments received until and including subframe N-4 in
order to determine whether OnDuration timer is running in subframe N, or in other
words, UE will consider assignments/grants received until and including subframe N-4
only, in order to determine whether in subframe N DRX Short cycle or DRX Long Cycle
is used and consequently whether OnDuration timer is running or not.
[0167] In a similar way the DRX-retransmission timer can be considered for the determination
whether to send CSI/SRS info at a specific subframe. Since UE starts DRX-retransmission
timer for the case that a transport block or PDSCH could not be decoded correctly
in order to monitor PDCCH for further retransmissions of the transport block, UE knows
already some subframes in advance whether DRX retransmission timer will be running
in a specific subframe. For example when UE should determine whether to transmit periodic
CSI/SRS at subframe N, UE knows already at subframe N-4 whether DRX-retransmission
timer will be running at subframe N since HARQ feedback for a potential PDSCH transmission
which might trigger the starting of DRX retransmission timer at subframe N would have
been sent in subframe N-4. For example in case a PDSCH transmission was scheduled
in subframe N-8 by a PDCCH which couldn't be correctly decoded, UE will sent a NACK
at subframe N-4. Hence, the UE and also eNB know that UE will start the DRX retransmission
timer at subframe N in order to monitor for potential retransmissions.
[0168] The above embodiment
has been explained and illustrated in the figures as if no processing time would be necessary
for the UE and the eNodeB to e.g. perform the estimation of whether or not to transmit
the CSI/SRS at subframe N or process incoming PDCCHs. Correspondingly, the above embodiment
was explained as if the processing took place "at subframe N-4". However, the UE and
eNodeB will need more time to decode the PDCCH, process the transport block of the
PDCCH, estimate the DRX-status of subframe N and of course also for preparing the
CSI/SRS. The processing may start at subframe N-4 and may well last for another one
or two subframes. The more important part is that although the estimation may actually
take place in e.g. subframe N-3 (e.g. due to processing delay), only information (e.g.
PDCCHs, DRX-timer values/status) until and including subframe N-4 are considered.
Therefore, the time between subframe N-4 and subframe N may be considered as a time
budget for the UE, to be used for amongst other: the decoding of the PDCCH, the processing
of the transport block of the PDSCH, the estimation according to the embodiment, the
preparation of the CSI/SRS (if transmission is to be done). This applies in a similar
manner to the remaining embodiments, explained below.
[0169] As explained above, the processing according to the first embodiment of the invention
(applies similarly also to the remaining embodiments explained below) may only need
to be performed four subframes before the subframe being configured for CSI and/or
SRS; i.e. at subframe N-4 for configured subframe N However, from the view-point of
implementation, the UE and/or eNodeB may also perform the estimation at every subframe
N, independently from whether or not periodic CSI and/or periodic SRS are even configured
for subframe N+4. Although this may lead to significant more processing, the complexity
of the UE and eNodeB can be reduced.
[0170] The following exemplary text, reflecting the above-explained first embodiment of
the invention, is suggested to be implemented in the 3GPP specification TS 36.321,
in section 5.7:
|
|
|
|
|
- if the PDCCH indicates a new transmission (DL or UL): |
|
|
|
- start or restart drx-InactivityTimer. |
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
received until and including subframe n-4 and onDurationTimer and drx-RetransmissionTimer would not be running according to grants/assignments received until and including
subframe n-4, type-0-triggered SRS [2] shall not be reported. |
|
- if CQI masking (cqi-Mask) is setup by upper layers: |
|
|
- in current subframe n, if onDurationTimer would not be running according to grants/assignments received until and including
subframe n-4, CQI/PMI/RI/PTI on PUCCH shall not be reported. |
|
- else: |
|
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
received until and including subframe n-4 and onDurationTimer and drx-RetransmissionTimer would not be running according to grants/assignments received until and including
subframe n-4, CQI/PMI/RI/PTI on PUCCH shall not be reported. |
Regardless of whether the UE is monitoring PDCCH or not, the UE receives and transmits
HARQ feedback and transmits type-1-triggered SRS [2] when such is expected. |
|
NOTE: The same active time applies to all activated serving cell(s). |
|
|
|
|
Second embodiment
[0171] The second embodiment of the invention deals with the problem that some unpredictable
UE behavior remains for the case of DRX MAC control elements being received by the
UE from the eNodeB, instructing the UE to enter DRX, i.e. to go into DRX mode and
thus become Non-Active. In other words, the eNodeB does not know which transmission
format will be used by the UE in subframe N, depending on whether or not CSI/SRS is
transmitted (e.g. Format 1 a vs Format 2a, see table for PUCCH format in background
section). This problem will be explained in more detail in connection with Fig. 13
and 14 illustrating DRX diagrams where a processing according to the first embodiment
is performed.
[0172] It is assumed that subframes N-10 and N are configured for periodic CSI/SRS transmission.
A PDCCH with a downlink resource assignment for a DRX MAC CE in the PDSCH is received
in subframe N-4, as well as the DRX MAC CE via the PDSCH. The DRX MAC CE is an instruction
from the eNodeB for the UE to enter DRX mode, i.e. to start e.g. the DRX-Short cycle
(not depicted). HARQ is applied to the PDSCH containing the DRX MAC CE, for which
reason the UE shall transmit a HARQ feedback (ACK/NACK) to the eNodeB at subframe
N.
[0173] However, the eNodeB does not know whether the UE received the DRX MAC CE sent in
subframe N-4 correctly, without decoding the HARQ feedback (ACK/NACK) at subframe
N. The estimation of the DRX status for the UE at subframe N depends on whether the
UE received the MAC CE correctly or not. In case the DRX MAC CE is received correctly
in subframe N-4, the UE goes into Non-Active Time as of subframe N-3 (ideally) and
thus transmits an ACK without reporting CSI and transmitting SRS in subframe N (see
Fig. 13).
[0174] In the other case, the UE fails to decode the DRX MAC CE correctly, thus stays in
Active Time and transmits a NACK and CSI/SRS in subframe N (see Fig. 14). Correspondingly,
the eNodeB still needs to implement double decoding to cover for the above-described
cases, which increases complexity of the eNodeB. A corresponding re-transmission of
the DRX MAC CE is performed at the earliest 8 subframes after the initial transmission
(according to configuration), and in the exemplary configuration of Fig. 14 is assumed
to be 9 subframes after initial transmission in subframe N+5. It is assumed that the
DRX MAC CE this time is decoded correctly, and thus the UE goes into DRX, Non-Active
Time.
[0175] According to the second embodiment, the estimation as to whether or not to transmit
the periodic CSI/SRS as configured considers only DRX MAC CEs received until and including
subframe N-(4+k), where k is an integer of 1 to K, and subframe N is the subframe
configured for periodic CSI and/or SRS. This ensures that the eNodeB knows in subframe
N already whether the DRX MAC was correctly received by the UE or not. It may thus
already know the transmission format used in subframe N.
[0176] Based on this estimation, a transmission of the periodic CSI and/or SRS is controlled
such that in case it is estimated that the UE will be in Active Time in subframe N,
CSI/SRS is transmitted, and in case it is estimated that the UE will be in Non-Active
Time in subframe N, CSI/SRS is not transmitted. Based on the scenario of Fig. 13 and
14, the result of applying the second embodiment of the invention is illustrated in
Fig. 15 and 16.
[0177] For the exemplary embodiment of Fig. 15 and Fig. 16, k=1 is assumed, such that only
DRX MAC CEs received by the UE until and including subframe N-5 are to be considered
for determining whether or not to transmit CSI/SRS as configured in subframe N. Thus,
as apparent from Fig. 15, DRX MAC CE received in subframe N-4 is not considered for
the estimation process, for which reason CSI/SRS is transmitted in subframe N together
with the HARQ feedback (in the example of Fig. 15, an ACK). The eNodeB, performing
the same determination and reaching the same result, expects the transmission of the
CSI/SRS and a HARQ feedback for the DRX MAC CE. No double decoding is necessary. (ACK/NACK
can be decoded without double decoding).
[0178] The exemplary scenario of Fig. 16 assumes that the DRX MAC CE (and the corresponding
PDCCH) is received in subframe N-5, instead of subframe N-4. It is further assumed
that the DRX MAC CE was correctly decoded by the UE, which thus exits the Active Time
and enters DRX Non-Active Time as of subframe N-4. According to the HARQ processing,
an ACK is transmitted from the UE to the eNodeB four subframes after the DRX MAC CE,
i.e. in subframe N-1. Correspondingly, the eNodeB receives the HARQ feedback (e.g.
ACK) and can deduce whether the DRX MAC CE was decoded correctly and applied by the
UE. Therefore, the UE estimates that it will be in Non-Active Time in subframe N based
on the correct reception of the DRX MAC CE, and thus does not transmit the periodic
CSI/SRS. The eNodeB, receiving the ACK, as HARQ feedback, also determines that the
UE will be in Non-Active Time in subframe and thus does not expect any reception of
the CSI/SRS.
[0179] Although the above explanation focused on k=1, i.e. considering DRX MAC CEs received
until and including subframe N-5, k may take other values too, such as 2, 3, 4 etc.
Using a higher k value increases the internal processing time available to the eNB
for processing the received HARQ feedback for a MAC CE and for deciding the expected
PUCCH format to properly detect and decode the PUCCH in subframe N.
[0180] Although the above second embodiment of the invention was described so far as a standalone
embodiment of the invention, being alternatively to the first embodiment, the second
embodiment and the first embodiment may well be combined. Correspondingly, the UE
estimates the DRX status of itself for subframe N, and thus also whether or not to
transmit the periodic CSI/SRS in subframe N based on:
- the UL grants and/or DL assignments received until and including subframe N-4 and
also on the DRX-related timers at subframe N-4 (as described for the first embodiment),
and
- the DRX MAC CEs received by the UE until and including subframe N-(4+k) (according
to the second embodiment.
[0181] Therefore, different subframe periods are used for considering grants/assignments
and the DRX-related timer and for considering the DRX MAC CEs.
[0182] Still alternatively, instead of also considering the DRX-related timers as explained
in connection with the first embodiment, the UE may estimate the DRX status of itself
in subframe N, and thus also whether or not to transmit the periodic CSI/SRS in subframe
N based on:
- the UL grants and/or DL assignments received until and including subframe N-4, and
- the DRX MAC CEs received by the UE until and including subframe N-(4+k) (according
to the second embodiment).
[0183] As already explained above for the first embodiment, the processing according to
the second embodiment of the invention may only need to be performed five (or N-(4+k))
subframes before the subframe being configured for CSI and/or SRS. However, from the
view-point of implementation, the UE and/or eNodeB may also perform the estimation
at every subframe N, independently from whether or not periodic CSI and/or periodic
SRS are even configured for subframe N+(4+k). Although this may lead to significant
more processing, the complexity of the UE and eNodeB can be reduced.
[0184] The following exemplary text, reflecting the above-explained second embodiment of
the invention, issuggested to be implemented in the 3GPP specification TS 36.321,
in section 5.7
|
|
- if the PDCCH indicates a new transmission (DL or UL): |
|
|
|
- start or restart drx-InactivityTimer. |
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
received until and including subframe n-4 and MAC Control elements received until and including subframe n-(4+k), type-0-triggered SRS [2] shall not be reported. |
|
- if CQI masking (cqi-Mask) is setup by upper layers: |
|
|
- in current subframe n, if onDurationTimer would not be running according to grants/assignments received until and including
subframe n-4, CQI/PMI/RI/PTI on PUCCH shall not be reported. |
|
- else: |
|
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
received until and including subframe n-4 and MAC Control elements received until and including subframe n-(4+k), CQI/PMI/RI/PTI on PUCCH shall not be reported. |
Regardless of whether the UE is monitoring PDCCH or not, the UE receives and transmits
HARQ feedback and transmits type-1-triggered SRS [2] when such is expected. |
|
NOTE: The same active time applies to all activated serving cell(s). |
Third embodiment
[0185] In contrast to the second embodiment according to which different time periods (N-(4+k)
vs N-4) were considered for the different kinds of information used for the determination
as to whether or not to transmit the CSI/SRS in subframe N, in the present third embodiment
the same time period (N-(4+k)) is assumed for all kinds of information as will be
explained in the following.
[0186] According to one variant of the previous second embodiment, DRX MAC control elements
that are received until and including subframe N-(4+k) are considered for the estimation
as well as UL grants/DL assignments received until and including subframe N-4; in
a further alternative variant DRX-related timers may be additionally considered for
the estimation to improve the estimation. Thus, information of different subframe
periods is used.
[0187] According to the third embodiment, information as available at subframe N-(4+k) is
used consistently for the estimation according to any of the above variants of the
second embodiment. Therefore, the present third embodiment of the invention is closely
related to any of the variants of the second embodiment, albeit changing the valid
time periods of the information considered for the estimation.
[0188] In particular, the UE and the eNodeB determine whether or not the UE is in Active
Time for subframe N and thus whether it shall transmit periodic CSI/SRS as configured
at subframe N based on UL grants / DL assignments received by the UE until and including
subframe N-(4+k) where k is a positive integer value of 1 to K. Likewise and as already
explained before, DRX MAC CEs received by the UE until and including subframe N-(4+k)
are also considered for the determination. In case DRX-related timers are additionally
considered for the estimation, the status of the DRX-related timers, e.g. DRX OnDuration
timer and DRX-retransmission timer, for subframe N estimated at subframe N-(4+k),
i.e. considering grants/assignments received until and including subframe N-(4+k),
are to be considered, rather than at subframe N-4 as before.
[0189] By using the same timing consideration of N-(4+k), the implementation of the invention
in the UE and the eNodeB is simplified.
[0190] The following exemplary text, reflecting the above-explained third embodiment of
the invention, is suggested to be implemented in the 3GPP specification TS 36.321,
in section 5.7
|
|
- if the PDCCH indicates a new transmission (DL or UL): |
|
|
|
- start or restart drx-InactivityTimer. |
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
and MAC Control elements received until and including subframe n-(4+k), type-0-triggered
SRS [2] shall not be reported. |
|
- if CQI masking (cqi-Mask) is setup by upper layers: |
|
|
- in current subframe n, if onDurationTimer would not be running according to grants/assignments received until and including
subframe n-4, CQI/PMI/RI/PTI on PUCCH shall not be reported. |
|
- else: |
|
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
and MAC control elements received until and including subframe n-(4+k), CQI/PMI/RI/PTI
on PUCCH shall not be reported. |
Regardless of whether the UE is monitoring PDCCH or not, the UE receives and transmits
HARQ feedback and transmits type-1-triggered SRS [2] when such is expected. |
|
NOTE: The same active time applies to all activated serving cell(s). |
Fourth Embodiment
[0191] The fourth embodiment of the invention deals also with the problem caused by the
reception of DRX MAC control elements, as already explained for the second embodiment
(see above). However, instead of considering DRX MAC CEs received by the UE until
and including subframe N-(4+k) according to the second embodiment, only DRX MAC CEs
are considered for the estimation for which an Acknowledgement (HARQ feedback) has
been sent from the UE to the eNodeB until and including subframe N-(3+k); k is a positive
integer from 1 to K. The advantage is that both the eNodeB and the UE have the same
understanding of what information is taken into account for determining whether to
send or not periodic CSI/SRS in subframe N. The fourth embodiment will be explained
in connection with Fig. 17 to 19.
[0192] As apparent from Fig. 17, k=1 is assumed for the exemplary illustrations of Fig.
17-19, such that only DRX MAC CEs are considered for which an ACK is fed back to the
eNodeB up to and including subframe N-4. Further, it is assumed that the PDCCH, indicating
the transmission for the DRX MAC CE on PDSCH, and the DRX MAC CE are received in subframe
N-8. Provided that the UE successfully detects the PDSCH, based on the PDCCH, and
decodes the DRX MAC CE, instructing the UE to enter DRX (i.e. Non-Active Time), the
UE will (ideally) enter DRX-mode and become Non-Active as of subframe N-7. This is
an ideal assumption as explained before; in reality a UE will only know at about subframe
N-5 that it has received in DRX MAC CE and can hence go to DRX Non-Active Time. Furthermore,
the UE will send the HARQ feedback ACK in subframe N-4.
[0193] The UE determines whether or not to transmit the periodic CSI/SRS as configured for
subframe N, based on the Acknowledgment for the DRX MAC CE sent at subframe N-4. Correspondingly,
the DRX MAC CE is acknowledged in subframe N-4, i.e. ACK is sent to the eNodeB, and
thus the UE determines that it will not transmit the CSI/SRS as configured in subframe
N, since it will be in Non-Active Time in subframe N. In a similar manner, the eNodeB
expects and receives the HARQ feedback ACK in subframe N-4, and thus determines that
the UE will not transmit the periodic CSI/SRS in subframe N. No double decoding is
necessary.
[0194] Fig. 18 is similar to the exemplary scenario in Fig. 17, with the difference that
it is assumed that the DRX MAC CE was not successfully decoded by the UE, which thus
transmits a NACK HARQ feedback to the eNodeB in subframe N-4, and stays Active accordingly.
Since no Acknowledgement was sent for the DRX MAC CE until and including subframe
N-4, but rather a NACK, the UE determines that it will send periodic CSI/SRS in subframe
N. The eNodeB reaches the same conclusion, since it receives the NACK of subframe
N-4 and thus learns that the UE could not decode and properly apply the DRX MAC CE.
[0195] As apparent from Fig. 18, the eNodeB after receiving the NACK for the DRX MAC CE
from the UE, retransmits the DRX MAC CE 9 subframes after the initial transmission.
After the retransmission, the UE is assumed to be able to decode the DRX MAC CE correctly
and to thus enter DRX mode, in particular Non-Active Time. A corresponding HARQ feedback
ACK for the retransmitted DRX MAC CE is transmitted in subframe N+5.
[0196] Fig. 19 illustrates an exemplary scenario, similar to the one of Fig. 17 and 18,
but with the significant difference that the DRX MAC CE is received in subframe N-7,
not subframe N-8. Correspondingly, the HARQ feedback for the reception of the DRX
MAC CE is transmitted from the UE to the eNodeB four subframes after the reception,
i.e. at subframe N-3, and thus outside of the window defined for being considered
for the determination of whether or not to transmit the periodic CSI/SRS in subframe
N. Therefore, the DRX MAC CE received by the UE in subframe N-7 is discarded for the
determination, although it is of course properly processed by other functions of the
UE. Therefore, for the determination of whether or not to transmit the periodic CSI/SRS
in subframe N, it is irrelevant whether the DRX MAC CE is successfully decoded or
not; only DRX MAC CEs are considered in said respect, for which an ACK is transmitted
until and including subframe N-4, which is not the case in the exemplary scenario
of Fig. 19.
[0197] Correspondingly, in case the UE is able to successfully process the DRX MAC CE it
will enter DRX, i.e. become Non-Active, but still has to transmit CSI/SRS in subframe
N, although it would not be in Active Time at subframe N according to DRX.
[0198] The following exemplary text, reflecting the above-explained fourth embodiment of
the invention, is suggested to be implemented in the 3GPP specification TS 36.321,
in section 5.7
|
|
- if the PDCCH indicates a new transmission (DL or UL): |
|
|
|
- start or restart drx-InactivityTimer. |
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
received until and including subframe n-4 and according to MAC Control elements for
which a HARQ feedback has been sent until and including subframe n-(3+k), type-0-triggered
SRS [2] shall not be reported. |
|
- if CQI masking (cqi-Mask) is setup by upper layers: |
|
|
- in current subframe n, if onDurationTimer would not be running according to grants/assignments received until and including
subframe n-4, CQI/PMI/RI/PTI on PUCCH shall not be reported. |
|
- else: |
|
|
- in current subframe n, if the UE would not be in Active Time according to grants/assignments
received until and including subframe n-4 and according to MAC Control elements for
which a HARQ feedback has been sent until and including subframe n-(3+k), CQI/PMI/RI/PTI
on PUCCH shall not be reported. |
Regardless of whether the UE is monitoring PDCCH or not, the UE receives and transmits
HARQ feedback and transmits type-1-triggered SRS [2] when such is expected. |
|
NOTE: The same active time applies to all activated serving cell(s). |
Fifth Embodiment
[0199] A further fifth embodiment of the invention considerably differs from the previous
embodiments, and mainly avoids the ambiguousness of the CSI/SRS transmission from
the UE in the transient phases, by considering a DRX status of a previous subframe
N-k for the determination of whether or not to transmit the periodic CSI/SRS in subframe
N.
[0200] In more detail, the UE shall transmit the periodic CSI and/or SRS to the eNodeB as
configured for subframe N, in case the UE is in Active Time in subframe N-k, where
k is a positive integer from 1 to K. This fifth embodiment provides a simple behavior
for the UE and eNodeB, but still ensuring predictability of the CSI/SRS transmission
to avoid the double decoding at the eNodeB.
[0201] k=4 is assumed for illustration purposes. Correspondingly, for the decision as to
whether or not to transmit the periodic CSI/SRS as configured for subframe N, the
UE takes the DRX status (i.e. Active Time or Non-Active Time) in subframe N-4 and
assumes for the determination same to be the DRX status of subframe N. Correspondingly,
based on the general rule that periodic CSI/SRS is only to be transmitted by the UE
when in Active Time, the UE can thus determine whether or not to transmit the periodic
CSI/SRS in subframe N based on the DRX status of subframe N-4.
[0202] Fig. 20 illustrates the exemplary scenario of Fig. 19, but with the fifth embodiment
applied, instead of applying the fourth embodiment. Accordingly, it is assumed that
a PDCCH and the DRX MAC CE indicated by the PDCCH,are received in subframe N-7, that
the UE correctly decodes the DRX MAC CE and thus (ideally) enters the DRX Non-Active
time as of subframe N-6. An Ack is transmitted as the HARQ feedback for the DRX MAC
CE in subframe N-3 to the eNodeB.
[0203] For determining whether to transmit the periodic CSI/SRS or not in subframe N, the
UE determines whether it is in Active Time in subframe N-4 or not. Since the UE is
not in Active Time in subframe N-4, due to the correctly decoded DRX MAC CE received
previously, the UE will determine not to transmit the CSI/SRS. The eNodeB makes the
similar determination and comes to the result that the UE will not transmit the CSI/SRS
since the UE is in Non-Active Time in subframe N-4, which is the relevant DRX status
for transmitting CSI/SRS in subframe N.
[0204] Although not depicted, when the DRX MAC CE is not correctly decoded by the UE, which
thus does not enter Non-Active time as of subframe N-6 but remains Active, the UE
will be in Active time in subframe N-4, and thus CSI/SRS will be reported at subframe
N as configured. Correspondingly, eNodeB comes to the same determination result, and
thus expects and receives the periodic CSI/SRS in subframe N.
[0205] This fifth embodiment reduces the complexity of the implementation for both the UE
and eNodeB, while solving the problem of avoiding double decoding at the eNodeB.
[0206] Although this alternative approach is more simple from the view point of implementation,
it should be noted that on the other hand, since only the DRX status of subframre
N-k is considered for deciding whether to transmit CSI/SRS in subframe N or not, the
usability of CSI/SRS info for scheduling might be reduced. The CSI/SRS reporting period
is basically shifted by k subframes compared to the DRX Active Time, i.e. CSI/SRS
reporting starts k subframes after DRX Active Time is started, and ends k subframes
after DRX Active Time ends.
[0207] The following exemplary text, reflecting the above-explained fifth embodiment of
the invention, is suggested to be implemented in the 3GPP specification TS 36.321,
in section 5.7
|
|
- if the PDCCH indicates a new transmission (DL or UL): |
|
|
|
- start or restart drx-InactivityTimer. |
|
- in current subframe n, if the UE was not in Active Time in subframe n-4, type-0-triggered
SRS [2] shall not be reported. |
|
- if CQI masking (cqi-Mask) is setup by upper layers: |
|
|
- in current subframe n, if on Duration Timer would not be running according to grants/assignments received until and including
subframe n-4, CQI/PMI/RI/PTI on PUCCH shall not be reported. |
|
- else: |
|
|
- in current subframe n, if the UE was not in Active Time in subframe n-4, CQI/PMI/RI/PTI
on PUCCH shall not be reported. |
Regardless of whether the UE is monitoring PDCCH or not, the UE receives and transmits
HARQ feedback and transmits type-1-triggered SRS [2] when such is expected. |
|
NOTE: The same active time applies to all activated serving cell(s). |
Hardware and Software Implementation of the Invention
[0208] Another embodiment of the invention relates to the implementation of the above described
various embodiments using hardware and software. In this connection the invention
provides a user equipment (mobile terminal) and a eNodeB (base station). The user
equipment is adapted to perform the methods described herein.
[0209] It is further recognized that the various embodiments of the invention may be implemented
or performed using computing devices (processors). A computing device or processor
may for example be general purpose processors, digital signal processors (DSP), application
specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other
programmable logic devices, etc. The various embodiments of the invention may also
be performed or embodied by a combination of these devices.
[0210] Further, the various embodiments of the invention may also be implemented by means
of software modules, which are executed by a processor or directly in hardware. Also
a combination of software modules and a hardware implementation may be possible. The
software modules may be stored on any kind of computer readable storage media, for
example RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc.
[0211] It should be further noted that the individual features of the different embodiments
of the invention may individually or in arbitrary combination be subject matter to
another invention.
[0212] It would be appreciated by a person skilled in the art that numerous variations and/or
modifications may be made to the present invention as shown in the specific embodiments
without departing from the spirit or scope of the invention as broadly described.
The present embodiments are, therefore, to be considered in all respects to be illustrative
and not restrictive.